When you look around you, you could see that there are objects that are moving in different ways and directions. Other objects are moving slow, others move fast. The reason that an object speeds up is there are forces that are applied to it.
For example, a train speeds up when leaving a station and, then, slows down when approaching another station. As we go further in this lesson we will learn how to easily describe the motion of an object.
Frame of Reference
You have learned that motion is a change in the position of an object over time. The motion of an object can be determined by observing it at a specific frame of reference or a fixed point of position. Therefore, to completely define the motion of an object, one should note the change in its position over time in relation to the frame of reference.
For example, the frame of reference in the illustration below is the edge of the table shown as point A. Since the ball’s position did not change with respect to the frame of reference, the ball is motionless, at rest, or stationary.
On the other hand, when the ball slowly rolled towards the edge of the table, shown in Figure 2 as point B, the ball moved away from the frame of reference which is point A. This shows that the ball was in motion when it rolled from point A to point B.
Motion Descriptors
Motion descriptors are terms used to describe objects that are in motion. These descriptors are enumerated below.
Distance tells how far two objects (or points) are from one another. It describes the total space covered by a moving object. It is usually expressed in centimeters, meters, and kilometers.
Displacement is distance with direction. It refers to how far an object travelled with respect to a frame of reference. It is the shortest distance covered by an object from the initial to its final position. Similar to distance, it is also expressed in centimeters, meters, and kilometers but with a specified direction.
Time is also an essential factor in describing motion. It refers to the duration of a period or how long an object is moving. Time is expressed in seconds, minutes, hours, or days. It plays an important role in determining how fast or slow a moving object is.
Speed refers to the rate of change in the position of a moving object. It measures how fast an object moves. It is calculated by determining how much distance was covered by a moving object over a certain period of time.
On the other hand, velocity is the speed with direction. It refers to the rate of change in the position of a moving object with respect to a frame of reference. It describes how fast and in what direction an object is moving. The velocity of an object is computed by dividing displacement by time.
Lastly, acceleration is the rate of change in velocity over a certain period of time. When there is a change in velocity, there is acceleration. Change in velocity occurs when a moving object speeds up, suddenly stops, or makes a turn. An object speeding up is experiencing acceleration while an object slowing down is undergoing deceleration. Acceleration is calculated by dividing the change in velocity by the change in time.
Interpreting Maps
Maps are highly useful tools in locating yourself in a specific place. Maps also serve as guides when traveling from one place to another. Reading a map is an important skill in determining distances and displacements.
In a running competition, racers position themselves first in the starting line. As the gun is fired, the race will start, and racers run as fast as they can to reach the finish line. Some runners may be behind others who are running fast, while those ahead may reach the finish line first. Based on the scenario, how can you say that the runners are in motion? What roles do distance and time play in motion? Let us find out in the following lesson.
To measure means to provide the exact size or quantity of an object or event using instruments with standard units. For example, instead of saying that the distance is far, it can be measured using a ruler or a meter stick and expressed in meters or kilometers. Instead of saying that an event took so long, time may be recorded using a stopwatch or a clock and expressed in seconds or minutes.
Measuring Distance
There are different instruments used in measuring distance. The most common tool in determining short distances or lengths is the ruler. It may come in various shapes and sizes, but its standard units are expressed in millimeters (mm), centimeters (cm), or inches (in).
A meter stick can measure distances up to one meter. It is usually marked in millimeters and centimeters. It is highly useful in measuring distances longer than a ruler. A yardstick often appears as a flat, thin, and rectangular wood or metal. It measures objects up to a yard which is equivalent to 3 feet long. A measuring tape is used for distances that are also too long for a ruler. Its main advantage is that it is very flexible and can be used around corners or curves. On the other hand, an odometer is used for huge distances such as those covered by vehicles. This instrument expresses distance in kilometers (km) or miles (mi). The odometer is usually installed on the car’s dashboard. It is for the driver to easily monitor the distance or mileage that the car has covered. This will give the driver an idea of how much it has traveled already, and if it has exceeded the maximum mileage it could cover since its manufacturing date.
Measuring Time
Time can be measured using an ordinary clock or watch, a digital timer, or a stopwatch. Such instruments express time in seconds (s), minutes (min), and hours (h). A stopwatch is a special kind of watch that can be digital or analog. It has start, stop, and reset buttons that are used to determine the exact duration of simultaneous events such as races. It helps in identifying who finished a certain task in a shorter amount of time. Although it is a common instrument used in sports, it is also found in laboratories, quiz bee competitions, and examinations.
In reading the time on an analog clock, it is important to distinguish its different hands and their purpose. The shorthand is known as the hour hand as it tells the hour, while the long hand is the minute hand which tells the minutes that pass by. There is another thin, long hand that moves the fastest as it tells the number of seconds.
An analog clock is divided into 12 sections. Each number on each section represents a specific hour. Between those numbers are tiny marks or lines wherein each mark is equivalent to 1 minute. The distance between each number is 5 minutes and the total number of minutes in a regular clock is 60 minutes. To read the time on the clock, start first with the short hand to tell the hour. Then, count the number of minutes by determining where the long hand is pointing.
An analog clock may also be used in counting the time in seconds. Each movement of the second hand is equivalent to one second. Similarly, each mark that the second-hand passes count as one second. One complete trip around the clock of the second hand is sixty (60) seconds which is equivalent to one minute.
Nowadays, different appliances and gadgets allow us to accomplish important tasks and to live comfortably. At home, sumptuous food is cooked with the help of an electric or a gas stove. Furthermore, information can be obtained in one click with the use of computers or mobile devices. You get to enjoy and relax during your free time watching television. These appliances mentioned are powered by electricity, and it eventually releases heat.
The applications of heat and electricity became possible because of the materials that allow heat and electricity to flow through them. In this lesson, you will find out what electricity is and what makes a material a good conductor and insulator of heat and electricity and their uses. Moreover, you will learn how black and colored objects affect the ability to absorb heat. Lastly, you will determine the harmful effects of heat and electricity and how to keep yourself safe when using them.
All things, living or not, are made up of atoms. Atoms are the building blocks of matter. It is a tiny particle that cannot be seen by the naked eye, even with an ordinary microscope. Also, it contains smaller particles that carry charges. The positively charged particles in an atom are known as protons, while the negatively charged particles are called electrons. The number of protons and electrons in an atom determines its charge, too. A neutral atom has the same number of protons and electrons. When an atom loses or gains electrons, the atom becomes charged. A charged atom has an unequal number of protons and electrons.
Electrons are loosely attached to atoms, and this enables them to move to other atoms. When an atom loses electrons, then it will have more protons than electrons. An atom that has a lesser number of electrons than protons is said to have a positive charge. On the other hand, an atom that gains electrons will have more electrons than protons and is said to have a negative charge.
It is easy to understand how electricity is produced when you realize that all materials are made up of atoms that have positively and negatively charged particles. Electricity can be described as the movement of electrons. When electrons move to other atoms causing an unequal number of protons and electrons, atoms become charged. When there are charged atoms, there is electricity.
Static Electricity
When you witness a lightning strike, you are looking at static electricity. Static electricity is the result of an imbalance in electric charges in an object. Have you experienced combing your hair and noticing that some of the strands seem to follow the comb once you take it away from your hair? Friction between the comb and the hair can rub electrons off from your hair to the atoms in the comb. This will result in the comb gaining electrons, making it negatively charged. Since your hair loses some electrons, it becomes positively charged.
Similar to magnets, like charges repel while opposite charges attract. In the given illustration, as the boy slides, some of the electrons on his body are transferred to the slide. This transfer of electrons made parts of his body like his hair stand. Since his hair strands are close to each other, they are positively charged. Thus, they will repel one another. The repulsion will result in the temporary standing of some of the hair strands. If the boy combs his hair, some electrons will move to positively charged atoms to become neutral.
Static electricity occurs when atoms build up charges. When atoms are charged, electrons move. Lightning happens because of the buildup of charges in clouds. You see lightning as electrons transfer to positively charged atoms.
Electric Current
Every time you turn on the light or switch on any appliance or electronic gadget, you use electricity. The form of electricity used in appliances, machines, and other electronic devices is known as electric current. Current means flow. Electric current can be described as flowing electrons.
Unlike static electricity, electric current can flow only through a material. The electrical wire serves as the pathway for electrons to flow. This flow of electrons is similar to falling domino bricks. One push on one brick pushes the next brick until all lined-up dominoes are toppled down.
Conductivity
Imagine a road with different pathways where vehicles are passing by. The said scenario is similar to how electricity is flowing. Electricity flows in a certain pathway until it reaches its destination that will make an object work. Conductors can be described as materials similar to pathways. A material is a conductor if it allows heat or electricity to travel through it. Conductivity describes how easily heat or electricity can transfer through a material. It is a measure that can be used to compare how good a material is as a conductor compared to others.
Heat energy is generated when particles move. Heat spreads throughout the material when there is an electric current because of the movement of electrons. Therefore, many electrical conductors are also conductors of heat.
Characteristics of Good Conductors
A material made of atoms with loose electrons will allow heat and electricity to flow. Metals are made up of atoms that have more loose electrons compared to other materials. This characteristic of metal made them good conductors of heat and electricity. However, metals differ in their conductivity. Some metals like silver, gold, copper, and aluminum have higher electrical conductivity compared to others. Their higher conductivity makes them good conductors of electricity. Take note that some non-metal materials can conduct heat and electricity. Water and your body are examples of non-metal objects that allow electricity to flow.
Common Uses of Conductors
Silver is used as contact parts of batteries and other conductive parts that need to be connected to equipment like watches, computers, and solar panels.
On the other hand, copper is commonly used in electrical wires because of its high conductivity, ductility, and abundance compared to silver.
Materials used for heating are chosen because of their good conductivity and their abundance. Silver is a good conductor of heat, but diamond is known to have a higher heat conductivity than silver. Copper, aluminum, and iron are more abundant than diamond, a lot cheaper to use, and are also good conductors of heat. They do not easily change as they transfer heat when used in cooking. If they are poor conductors, it will take more time for food to cook, or they might change shape or melt because of the heat.
Absorption of Heat
Light has different components as well as the colors of the rainbow. When light passes through a white-colored object, all the colors of light bounce off the object, and you see the white color. When light passes through a black object, all the light is absorbed, and no color bounces off the object. Hence, you see only black color.
When light is absorbed by an object, it interacts with the atoms of the object. Thus, making the atoms move. Atoms bumping each other generates heat. Since a black object absorbs all the light, its temperature increases faster than any other colored object.
The discovery of the use of heat and electricity has improved the lives of people throughout history. The applications of heat and electricity became possible because of the materials that allow heat and electricity to flow through them. Choosing the right materials to use with heat and electricity allows for its safe and proper use.
Most of the cooking pots and pans are made up of metals, so the stove’s heat can easily be conducted to the food it is cooking. Most of the time, handles are made up of wood, plastic, or rubber. This is to prevent the heat from flowing easily to handles which are necessary for the person to hold it while cooking.
Have you noticed that all the electrical wires you use at home, from charger cables to appliance cables, are covered in plastic or rubber? Why are electrical wirings wrapped with those kinds of materials? There are materials that are opposite to conductors in which they do not allow heat and electricity to pass through them. What materials do not allow heat and electricity to flow?
A material that does not allow electrons to flow is called an electrical insulator. Electrical insulators are materials made of atoms that do not have loose electrons. On the other hand, a material that does not allow heat to flow is called a heat insulator. These materials do not transfer heat throughout their surface easily. Plastic, glass, cloth, and wood are examples of both electrical and heat insulators.
Characteristics of Good Electrical and Heat Insulators
Good electrical insulators prevent electric current from traveling through them. Insulators are used to cover electrical wires to prevent the flow of electrons to other conductors such as water and the human body. If wires are not insulated, electricity can be conducted from the wire to your body if you touch it.
Good electrical insulators are not always good heat insulators. Plastic and rubber are heat insulators, therefore, heat does not easily spread on these materials. However, too much heat can change some types of plastic and rubber easily by melting them. There are also types of glass that crack when heated, so not all glass are good insulators of heat.
Good heat insulators are heat resistant. Being heat resistant is similar to being heat proof, wherein the material does not become hot easily even if it is exposed to heat. Good insulators are heat resistant. These are materials that do not allow heat to travel through them, and do not change easily. Also, such materials are used to make lunch boxes and water bottles that can maintain the temperature of food or water inside them. In insulated containers, the heat from the hot food does not transfer to the air outside the container. In the same way, heat from the air outside does not transfer to the cold food or drink inside the container.
Do you notice the materials used in drinking coasters, pot place holders, and ladle handles? Insulators such as plastic, rubber, cloth, and wood are usually found in parts of those objects. These materials keep heat from traveling to your hands when handling hot objects.
Silicone and polystyrene are examples of plastic that are good insulators. Silicone is used in electrical wires, cooking, and baking because of its electrical and heat insulating properties.
Polystyrene is commonly used to make packaging materials. One popular brand of polystyrene is styrofoam. Fresh meat, fish, and ice are commonly packed in polystyrene boxes when transported from the source to the markets. They maintain the freshness of food and prevent ice from melting by keeping heat away from the inside of the box.
Using Heat and Electricity
Electricity is the energy used to run all industries that exist today, from manufacturing to entertainment. It can be transported to specific areas through wires to make it useful for so many purposes in any area. Factories rely on electricity to operate machines. Buildings and homes use electricity for light, air cooling or warming, appliances, and many more. Electricity is also necessary for the field of transportation and entertainment.
Heat is used in many industries such as mining, electricity generation, manufacturing, transportation, and food. Heat is used in buildings and homes for controlling the temperature inside, for cooking, and for drying.
Dangers in Using Heat
Heat can cause burns in the body. Depending on the intensity of heat and the length of time the body is exposed to it, burns can be severe. In the worst cases, they can be deadly. Contact between heat from objects and the skin can cause burns. On the other hand, contact between heat from objects and flammable objects can cause a fire. Flammable objects are those that can easily ignite or burn such as dried leaves, paper, oil, and alcohol.
Electricity carries heat with it as it travels through wires. Overheating of electrical devices can cause a fire. Fire can form if there is enough heat, oxygen, and something that can burn (fuel). Fire can cause damage or loss of property, injuries, and death.
Dangers in Using Electricity
Electricity can be harmful if not used with proper care. If you have experienced accidentally touching an exposed wire while it is plugged, you are aware of how unpleasant that can be. An electrical wire that is not covered by an insulator is referred to as exposed. A live wire describes a wire carrying an electric current. If your body comes in contact with a live and exposed wire, you are allowing your body to become a conductor of electricity. The effect can be mild to deadly.
An electric shock can be experienced by a person that comes directly in contact with a live wire. The effects of electric shock depend mainly on how much electricity passes through the body. The effects range from a startling tingling sensation that can be painful, minor or major burns due to heat carried with electricity, and damage to internal organs. In worst cases, electric shock can lead to electrocution or death by electric shock.
Safety Measures in Using Heat and Electricity
Hazards are conditions that can possibly cause harm or lead to accidents. In order to reduce the hazards of heat and electricity, it is important to take note of the following:
Safety Measure
For heat hazards:
Make sure to use insulated pads, gloves or mittens when handling hot objects such as pots and pans.
Stay focused when cooking and baking. Do not leave food unattended while they are being heated.
Keep flammable objects (e.g., paper, alcohol, and oil) away from a heat source.
For electricity hazards:
Before plugging and using appliances, check if the wires are completely insulated and there are no exposed parts of the wire.
Never touch the metal parts of the plug.
Unplug appliances, devices and chargers when not in use. Do not leave charging devices unattended.
Do not plug in too many devices at the same time.
Do not touch electrical appliances with wet hands.
During rainy weather, wear rubber-soled covered shoes when it is unavoidable to walk on wet streets.
Report immediately to adults if you smell something near the wires, or notice sparks coming off the wires.
Light is essential in our life. We cannot see things if there is no light around us. The light could be from a natural source, such as the sun. Otherwise, it could also be from the candles, light bulbs, and such. Brightness, darkness, contrast, and colors are all made possible because of light. Your eyes are designed to sense the effects of light as it interacts with the things around you. Light interacts with objects in its path. Whether you see a shadow or a reflection depends on the behavior of light as it hits an object. In this lesson, you will understand how light behaves when it encounters an object in its path.
Light travels in a straight line. Hence, it cannot go around an object that blocks its way. Light behaves in various ways, depending on the material that blocks its way. Light can be reflected, refracted, absorbed, and transmitted as it interacts with different kinds of objects.
Reflection
Reflection is the bouncing of light. When the reflected light reaches your eyes, it passes through the lens of your eyes. The lens of your eyes creates an image of the object at the part of your eye called the retina. The optic nerve behind the retina sends a message to the brain about the image. The brain interprets the image as the object that you see. Although seeing involves several processes, you can identify an image instantly because sending messages to and from the brain happens rapidly.
Light can reflect from different kinds of surfaces. Light reflects and produces an image on smooth, polished surfaces like mirrors. Light may also be reflected from still, undisturbed clear water like ponds or rivers. For some objects that reflect light, an image forms in the eyes but not on the object’s surface. You can see an image as an actual representation of the object in front of you through reflection. For instance, when you face a mirror, you see an image of yourself that is laterally inverted or an image that is inverted from left to right.
Refraction
Refraction is the bending of light. This happens when the speed of light changes as it travels from one medium to another. An example would be light traveling from air to water. Since water is denser than air, the light changes its direction and becomes slower as it travels through the water. Have you noticed the things that are submerged in the swimming pool while you are on the poolside? Refraction can result in images that may be different in size and shape than the actual object.
Lens is a transparent material that refracts light and produces an image. A lens can be convex or concave. The image produced by a lens can be bigger or smaller than the actual object depending on its shape.
Absorption
Light can also be absorbed by a material. However, it will not be reflected. Instead, it will be converted into heat. This process is called the absorption of light energy. White objects reflect all the colors of light, while black objects absorb all light that hits them. Thus, black objects heat up faster than any other colored object.
Transmission
Light is transmitted when it is allowed to pass through an object. The transmission of light depends on the material that it interacts with. These materials can be classified based on how they transmit light. Transparent materials can transmit all the light. You can see through a transparent object because it is clear, so all the light can easily pass through it. Glass windows and water are examples of transparent objects.
Translucent materials can transmit only some light. You can see through a translucent material but not as clear compared to a transparent material. Tea drink, stained glass, and sunglasses are examples of translucent objects.
Opaque materials do not transmit light. Instead, they block the passage of light. A rock is an example of opaque material. When light rays hit the rock, some parts of it are reflected. Therefore, this allows us to see the rock. On the other hand, some parts of the light are absorbed, which heats the rock when exposed to the sun.
Realizing how different objects transmit light allows one to know which type of material will be used for a certain purpose. For instance, choosing a type of material in making windows depends on how much light you would like to be transmitted inside your house.
Transparent windows transmit all the light, allowing you to see things clearly from the inside. Translucent windows transmit only some light. Thus, images from the inside are blurred. Lastly, the light will not be transmitted in a closed wood window cover.
Shadows form when the light is blocked. They are formed in areas where light is not transmitted. Opaque and translucent objects form shadows when they are in the path of light. Opaque objects have darker shadows than translucent objects because not all light is blocked by translucent objects.
Colors could help us describe or identify specific objects. It could also be a symbol of our emotions. The things around you come in different colors, like the blue sky, green grass, and red fruit. The light that comes from the sun does not seem to be colorful, but it allows you to see a colorful world. Why do you see different colors?
The electromagnetic spectrum is composed of various electromagnetic waves such as X-rays, infrared radiation, and ultraviolet radiation. The visible portion of the electromagnetic spectrum is called visible light. It refers to the light that is visible to the human eye. When all the colors of visible light are combined, white light is produced. Sunlight is an example of white light as it is made up of different colors of visible light. These colors are red, orange, yellow, green, blue, indigo, and violet, which you can see when a rainbow appears. Other examples of light sources that produce white light are fluorescent lamps and LED bulbs.
Since white light is a combination of different colors of light, its components can be separated as it passes through another object. Dispersion of light refers to the separation of white light into its component colors. A prism is a transparent object that disperses white light into different colors. Water droplets in the atmosphere can function as prisms to sunlight resulting in the occurrence of a rainbow.
Dispersion happens when white light enters a prism at an angle. Different colors of visible light slow down from different speeds as they travel through the prism. The different speeds of each color cause them to bend differently and separate from each other as they exit through the prism. Red is the fastest and the least bent color. On the other hand, violet is the slowest and the most bent color. The colors of visible light are arranged from fastest to slowest: red, orange, yellow, green, blue, indigo, and violet (ROYGBIV).
Reflection and Absorption of Colors
When white light hits an opaque object, some colors are reflected while some are absorbed. The parts of the white light that are absorbed will be converted to heat. The parts that are reflected and reach your eyes are the colors that you see. Study the figure below.
Sunlight appears white, but it is made up of different colors of visible light. Look at the illustration below. When white light reaches the red flowers, all the colors of the visible light are absorbed except for red. Red is reflected and reaches your eyes, so you see the flowers as the color red. In the same way, the leaves appear green because green is reflected, while it absorbs the other colors of the visible light. The colors that you see are the ones that are reflected from the object.
What happens if an object absorbs all white light? All light will be converted to heat. The object will not be able to reflect any color, and you will see the object as the color black. Take note that black is not part of the visible light. In other words, black is not a color but an absence of color.
What happens if an object reflects all the colors of visible light? The combination of all the colors of visible light makes an object appear to be white. A white object does not absorb any color but rather reflects all the colors of visible light. If no color is absorbed, then no light will be converted to heat. Take note that white is not a color, but the combination of all the colors of visible light.
Sound is everywhere. Even the simple chirping of birds, whooshing of air, and movement of some objects are considered sound. Sound is produced when vibrations from a source travel in a medium and reach the ears of a listener. The medium of sound can be a solid, liquid, or gas. Do you notice a difference in the sound of a basketball thrown on a wall and on a bed? The sounds you hear may vary depending on what the sound wave hits as it travels. How does sound behave when it encounters an object in its path?
Sound travels in waves. When sound waves hit an object, they can be reflected, absorbed, or transmitted by the material. Sound can also be refracted as it travels between two kinds of materials. In most materials, sound waves are partly reflected, absorbed, and transmitted.
Reflection
When a sound wave hits a hard surface, and cannot pass through, the sound bounces back. The bouncing back of the sound is called sound reflection. When a reflected sound bounces back towards the source, an echo can occur. Echo is a repeated sound reflected from a hard surface.
When sound is reflected from the hard surface of a smaller space, the sound may bounce off walls several times, producing multiple echoes. This kind of reflected sound is called reverberation. You will not hear it as an echo, instead, you may notice that the sound becomes longer. You may have experienced this kind of sound when you are inside an auditorium, a church, or a tunnel.
Echolocation is the use of reflected sound to locate an object. Some animals such as bats, dolphins, whales, and some birds use echolocation. It helps them find their way and search for food. Bats make ultrasonic sounds using their mouth, nose, or both. When the sound is reflected to them, bats can know exactly where the object is. This allows them to fly without bumping into objects while they hunt for food.
Refraction
Since sound travels in waves, it is also possible for waves to bend when they hit mediums with different temperatures. Sound waves change speed as they travel through the air at different temperatures. This is why sounds can be heard louder and clearer during a cold night, compared to a hot day.
Dduring the daytime, the air near the ground is warmer, and the air particles are less dense. In that condition, sound waves are refracted away from the warm air and bent upward towards the cooler air high above the ground. When a bell chimes from a clock tower, the person may not hear the sound from a distance.
When the air near the ground is cooler than the warm air above, sound waves bend downward. The chimes become loud because the direction of the wave shifted towards the cooler ground. Sound waves that bend towards the cooler night air allow people at ground level to hear the sounds clearly.
Absorption and Transmission
When a sound wave encounters an object as it travels, it can be reflected, absorbed, or transmitted, depending on the material. Materials that are soft absorb sound better than rigid materials. Also, uneven and porous surfaces absorb sound better than smooth materials.
When sound hits a soft material like a pillow, most of the sound is absorbed. The absorbed sound is converted to heat energy, similar to what happens when an object absorbs light. You may still hear some sounds through the pillow, but those sounds are softer or less clear because not all sound waves are transmitted by the pillow. Only the sound waves that are not absorbed are transmitted through the material.
Sound is transmitted by objects that allow sound waves to pass through the material. Do you hear sounds outside your room even if the doors and windows are closed? If yes, then the materials that make up your door and walls transmit sound that is not reflected or absorbed from the outside of your room. The transmission of sound also depends on the thickness of the material. Sound can travel faster through thinner materials.
The walls and ceilings of movie theaters are usually covered with curtains and other decorative fabric. The seats are also made of soft cushions covered in fabric. Those materials help absorb the sound that travels through it, while reducing reflection and transmission of sound. Those conditions help to produce clear, high-quality sounds inside the theater.
If you enjoy watching movies and listening to music, you are aware that people are able to use light and sound not only for observation and awareness. Light and sound are being used in different ways for the advancement of society. How do light and sound improve the lives of people?
Light in Homes and Common Areas
Natural sources of light include the sun and other stars. These natural sources of light may limit man’s actions depending on the place, time, season, and weather. The invention of artificial lights allows people to see things in dark places and increase their safety from dangerous areas.
Artificial lights enable people to extend their working and socializing hours. Furthermore, light is also used not only for basic lighting needs but also for communications and entertainment.
Aside from using artificial lights to see objects and the surroundings, people learned to use light to produce different kinds of images. Lenses, mirrors, and other materials use different colors of visible light to project images in devices such as television screens, projector screens, and cameras.
Examples of Light Technology Used in Different Industries
Telescopes and microscopes both use lenses that allow exploration and investigation of objects that are very far from the Earth or objects that are too small for the naked eye.
The LASER or Light Amplification by Stimulated Emission of Radiation is a narrow and focused beam of light that can be used for different purposes. It can be used as a tool for cutting very hard objects including metals and rocks. It can also be used in performing medical procedures like surgery.
Fiber optics is glass that is made into a transparent wire-like material. Fiber optic is used to guide light that carries information faster, over long distances. Light carries information such as voice, video, and other data. Since light travels very fast, fiber optic technology allows the fastest and most convenient communication.
Sound Technologies
Sound can be classified as pleasant or unpleasant. Unpleasant sound is also described as noise. Noise can be harmful physically and emotionally. It can damage ears, create a feeling of stress, and sometimes even fear. On the other hand, pleasant sounds make people feel calm or happy.
The behavior and properties of sound made it possible to develop technologies that improve the quality of life. People created ways to reduce or remove unpleasant sounds. There are also creations that produce pleasant sounds such as music.
Sound absorbing materials line the walls of music studios. The special materials prevent the transmission of unwanted sound into the room while music is being recorded. The sound that is being recorded should be clear and without any echoes.
Headphones with noise-canceling technology bump off sound waves outside the earpieces to prevent sounds from getting into your ears other than your music.
Musical instruments are designed using materials that can change the frequency of sound waves. Changing the frequency of sound allows people to create music using different notes.
Sound frequency is also being used in areas other than music. Ultrasonic frequency is also known as ultrasound. Ultrasound which is too high for humans to detect can be produced using man-made devices. In medicine, the reflection of ultrasound is being used to produce images of internal body parts.
Electricity is a form of energy that plays a vital role in this modern world. Life may be inconceivable without it. It usually comes from power plants or stations where electricity is generated. Electricity is used to light homes, buildings, and roads. It also plays an important role in making our appliances function. Most of these electric devices are controlled by a switch. When you turn on the switch, the electric device automatically starts to function. How does electricity flow to an electric device?
Electric current is the movement of electrons along a path that flows from negative to positive. The path in which the current flows is called a circuit. Electricity flows in a circuit when there is a source and when the path is complete.
Components of a Circuit
An electric circuit includes the following parts:
a. source or supply – an object which provides the necessary energy to make electricity flow (e.g., battery)
b. load – an object that uses the electric energy (e.g., bulb, motor in an appliance)
c. conductor – a wire or a cable in which the electricity runs through and links the source with the load (e.g., copper wire)
d. switch – a controlling device that is used to open or close the electric circuit
Open and Closed Circuit
An electric circuit may be described based on the flow of electric current in it. In this figure, electricity flows from the negative terminal of the battery to its positive terminal. Notice that the wires are attached to both ends of the battery and to the metal screws of the bulb socket where the bulb is tightly screwed. Through this connection, the electric current from the battery can flow completely up to the bulb, allowing it to light up. This shows a closed circuit. In a closed circuit, electricity flows completely. Thus, allowing the object to function.
On the other hand, this figure shows a wire disconnected from one screw of the bulb socket. However, the bulb does not light up in this kind of circuit because of the gap between the wire and the terminal (end) of the bulb. This is an example of an open circuit, where the flow of electricity is interrupted due to the break in the path of the circuit.
What do you think will happen if you touch the screw of the bulb socket? Will the electricity flow on you? The answer is no. This is because even if your hand is considered as a conductor, the circuit remains open as long as it is not connected to the battery. However, if you happen to touch one of the screws of the bulb socket and the end of the wire connected to the battery, the circuit is closed. Therefore, the electricity will completely flow from the positive terminal of the battery to the bulb to your hands then to the wires going to the negative terminal of the battery. Thus, this will make you experience a slight electrical shock. Consequently, touching an open circuit with bare hands can increase the chances of electrical shocks as it will close the circuit and complete the flow of electricity.
Short Circuit
A short circuit happens when two or more wires that are not supposed to be touching each other become in contact. The path of electricity flow becomes shorter, which leads to a higher amount of electricity flowing in a certain direction.
Since there is no load in the path where electricity flows in a short circuit, the electricity builds up in this direction. This causes overheating, which results in the melting of wires, formation of sparks with smoke, and sometimes it leads to a fire.
Roles of Switches
Switches are used in electric devices to open or close the circuit. It simply turns on or off the flow of electricity in a circuit. For example, when you turn on the switch of a certain device, the circuit is closed. The conductor from the switch becomes connected to the wire, allowing the electricity to flow completely. When you shut down the device, you turn the switch off to open the circuit. By opening the circuit, the flow of electricity is interrupted, disabling the electrical device to work.
As you have learned, a light bulb is a load in a circuit. There are more than one load or electric device in most electric circuits. These loads or electric devices can be connected in series or parallel circuits.
Series Circuit
In a series circuit, electric current flows through all the electric devices in one path. This figure shows an example of a series circuit where bulbs are connected one after another in a single chain. The bulbs are connected to the battery through wires. Moreover, the electric current travels from the negative end of the battery, then continues through the bulbs and back to the positive end of the battery.
The bulbs have the same brightness in a series circuit because the same amount of electric current passes through each load. But, if another bulb is added to the circuit, all the bulbs will be dimmer because the same amount of current has to do more work. What happens if one of the bulbs gets busted or removed?
Since electric current flows through a single path, when one bulb gets busted or removed, all the other bulbs in the circuit will not light anymore. The busted or loosened bulb opens the pathway, so the flow of electric current stops. Replacing the busted bulb will close the circuit making the other bulbs light up again.
Applications of Series Circuit
A ceiling lamp décor often uses a series circuit. This is to ensure the same amount of brightness for each bulb when electricity passes through it. You will know that a ceiling lamp décor has a busted part when it is not lit, even if you turn it on. Also, most refrigerators use a series system. Its wirings are connected in such a way that the electric current will flow in one path.
Parallel Circuit
In a parallel circuit, each bulb is connected to the battery separately. Therefore, each bulb is a part of a different circuit. Unlike a series circuit, the electric current flows through more than one path in a parallel circuit.
Some amount of the current available from the source (battery) flows along each path and through each light bulb. Each bulb in the circuit uses only the amount of current it needs enough to light up to its full brightness.
But, what happens if you remove one bulb or it gets busted? In a parallel circuit, when one bulb is loosened, taken out, or burned out, the other bulbs still light up since each bulb has its own pathway.
The break in one pathway does not affect the other bulbs because the electric current can still flow through the other paths and maintain a complete circuit. If you want to turn on or off each bulb without affecting others, you can place switches along each path in the circuit.
If you add more batteries to a circuit, there will be more electric current flowing in it. The bulbs can be brighter than their usual brightness when more than one battery is attached to them. However, there is also a tendency for the bulbs to be busted and disable them to light up. Most bulbs have limited capacity in terms of the amount of electric current they can handle. If there is too much electric current flowing in a circuit, the load in it might not handle it and eventually burn or explode. Therefore, the brightness of the bulb depends on the number of the source in the circuit, as well as the number of loads in it.
Applications of Parallel Circuit
Most lighting systems at homes, offices, or even on the streets use parallel circuits. Moreover, it saves money because if one light is busted, the rest of the lights will still work. Likewise, it is more practical to use parallel circuits for light systems since not all spaces at home require to be lighted at the same time.
Parallel circuits are also used in receptacle outlets. When both appliances are plugged into outlets, the electric current flows in each appliance. Even if one appliance is unplugged, the other appliance will still work because the flow of the electric current is uninterrupted.
In a junk shop, metal scraps are separated from other nonmetal junk with the help of machinery which uses magnets. However, the magnets used in such types of machinery are not the same as the magnets that you see around. It uses a certain amount of electricity for it to function. Without electricity, it lacks a magnetic field which is necessary to attract magnetic objects.
When you rub an iron nail on a bar magnet for quite some time and let it touch another magnetic object, you will notice that an attraction exists between the two objects for a short period of time. This is because a temporary magnet was made after the iron nail experiences the magnetic field from the bar magnet. But did you know that there is another way to create a temporary magnet? Electricity may be used to create temporary magnets. How can you utilize electricity to produce magnets?
One of the innovations in the field of transportation is the use of magnetic levitation as the key concept in running high-speed trains. Trains that apply the magnetic levitation concept are known as maglev trains, wherein man-made magnets or electromagnets are used to help them move swiftly. The maglev trains are floating with the help of electromagnets on the sides of the track instead of running on a usual steel track. This is just one of the many uses of electromagnets in various industries.
Electromagnets
Electromagnets are man-made magnets that produce a magnetic field using electricity. A simple electromagnet is made by using a battery, copper wire, and iron nail. In creating an electromagnet, the wire must be looped around the nail. Also, its ends must be connected to the terminal of the battery. The looped wire is called a coil, while the nail is known as the core. Likewise, the battery serves as a source of electricity.
The electric current or also known as the moving electrons will flow through the coil when its ends are attached to both sides of the battery. Flowing electricity creates a magnetic field around the coil that is transferred to the nail. This magnetic field pulls near magnetic objects toward it.
Unlike natural magnets, the magnetic field of an electromagnet is temporary. When the electricity stops flowing through the coil, the electromagnet will also stop working. But similar to natural magnets, electromagnets have north and south poles too. Since the electric current flowing in an electromagnet moves in a definite direction, the magnetic field created around the conductor is definite too. Therefore, the north and the south pole may be identified depending on the flow of the electric current in the electromagnet.
Uses of Electromagnets
Most appliances at home are operated through motors. A motor is a machine that uses electricity and an electromagnet to operate different appliances. Examples of these appliances are electric fans, refrigerators, and washing machines.
Speakers and headphones are common sound devices used to hear music or different sounds. An electromagnet is placed in front of a natural magnet inside a speaker. Thus, it causes the speaker to produce sound.
Electromagnets are also used in transportation. In some countries, Maglev trains are used as public transportation. To better understand how it works, imagine a box with magnets on the four bottom corners and a special railway made with magnets. The magnets have the same poles, which causes the train to float or levitate.
Other means of transportation that are commonly used are cars and motorcycles. These vehicles move through engines or a type of motor that functions with the help of electricity and fuel. Engines use electromagnets to make cars and motorcycles move.
In the field of medicine, electromagnets play an important role too. An example of equipment being used is magnetic resonance imaging (MRI). It is a machine used to scan the human body and create detailed images of the inner body parts. These images help doctors examine the organs of the human body, which helps detect various injuries or illnesses.
Did you know that most of our devices and appliances at home have electromagnets? It can be seen in earphones, speakers, motors, and generators. Moreover, its wide applications are evident in communication, entertainment, transportation, and medicine. Have you ever wondered how big are the electromagnets used in a maglev train and a car? Does the size of
the electromagnet affect its capacity to work on bigger objects? Electromagnets have different pulling forces or magnetic strengths. In this lesson, you will learn the different factors affecting the strength of an electromagnet.
Effects of Coil Used
One way to strengthen or lessen the magnetic field of an electromagnet is to change the number of coils of wire around the core. When more coils are added, the magnetic field becomes stronger. Remember that coils act as a conductor around the nail where the magnetic field is formed. The more coils surround the nail, the greater electricity flows on it. Thus, creating a stronger magnetic field. On the other hand, when coils are lessened or removed, the magnetic field becomes weaker.
The number of coils affects the strength of an electromagnet. What happens when the coils are pushed closer together?
The distance between coils affects the flow of electricity in an electromagnet. The magnetic field produced in an electromagnet is dependent on the amount of electric current that flows on it. The greater the distance between coils, the lesser the electricity flows on the core. Thus, the electromagnet is weaker. This also means that when coils are pushed closer together, electricity flow increases, producing a stronger magnetic field.
Effects of Core Used
The core used in an electromagnet also affects its strength. The illustration below shows two simple electromagnets, one with a thin core and a thick core. Which one has a stronger magnetic field?
The blue curve lines represent the magnetic field lines of an electromagnet. The electromagnet with a thick iron core produces a greater magnetic field than a thin core. Having a thicker core enables it to conduct more electricity which is essential in producing a magnetic field. The thin core accommodates lesser magnetic field lines, while the thick core accommodates more magnetic field lines. This means that an electromagnet with a thicker core is stronger than an electromagnet with a thin core.
Effects of Electricity Supply
You have already learned that electricity flow affects the strength of an electromagnet. Another way to strengthen a simple electromagnet is by changing or adding batteries. A battery is a device that supplies a certain amount of electricity. The amount of electricity being supplied by a battery depends on its type and size.
A battery that produces a greater amount of electricity also produces a stronger magnetic field through the coil. Since electricity is the main factor in making the electromagnet stronger, you may add batteries to your electromagnet to strengthen its magnetic field.