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Title: Completing the Circuit
Principle(s) Investigated: Chemical Reactions, Systems, Energy Flow, Electricity, Ohm's Law, Conservation of Energy
Standards:
SEPs: Asking Questions, Developing and Using Models, Constructing Explanations and Designing Solutions.
DCIs: PS3.B: Conservation of Energy and Energy Transfer, PS3.D: Energy in Chemical Processes and Everyday Life
CCCs: Systems and System Models, Energy and Matter (Flows, Cycles, and Conservation), Cause and Effect: Mechanism and Explanation
Materials:
D Battery 1.5v (1 per group)
Battery Pack (1 per group)
E10 Miniature Screw Base Light Bulbs (1.5V)
Alligator Clips (2 per group)
Probe 10 (1 per person)
Data Response Sheet (1 per person)
Procedure:
1) Observe the list of possible combinations to complete the circuit.
2) Use Probe 10 to predict which methods will be successful in completing the circuit and lighting the lightbulb. Indicate if you think the bulb will light up by circling the corresponding letter.
3) With your partner, use the materials given and test your predictions.
4) As you test, identify which methods were successful and which were unsuccessful. Check the appropriate boxes on your data sheet as you test the 8 given combinations. Do not change your predictions on Probe 10.
5) Draw a model representing the flow of energy and how the flow of electrons passes through the components of the system, including how energy is transformed.
6) Extension Activity- For those who finish the other testing early, take away one alligator clip and see if they can light the bulb using only the battery, light bulb, and one alligator clip.
Student prior knowledge:
Students will have already been taught and have a solid understanding of systems (inputs, outputs, components, etc). Students will have previous knowledge of energy flow from previous learning segments, but this segment serves as an introduction to the concept of electricity flow and utilizes background, previous knowledge to assess student understanding of electricity flow.
Explanation:
In order for the circuit to be complete, the end of one alligator clip must touch the negative node of the battery and a corresponding portion of the lightbulb (Electrical foot contact OR screw thread contact. Simultaneously, the other alligator clip must touch the positive node of the battery and the other portion of the lightbulb (Electrical foot contact OR screw thread contact). For electrons to do their job in producing light, there must be a complete circuit so that they can flow in to a light bulb and then be able to flow back to their original power source. Hence, if you break the connection on either node of the battery, or the connection to the corresponding parts at the base of a lightbulb, electrons are unable to flow in a cycle to produce light. The flow of energy is as follows, electrons flow out of the negative terminal of the battery, through the wires into the corresponding portion of the lightbulb, through the bulb and filament which produces the light, then through the second wire into the positive terminal of the battery so that the circuit can be completed.
Ohm's Law demonstrates the relationship between voltage, current, and resistance that is crucial for understanding electricity and identifying the amount of voltage required to power an object. Electrical power in a circuit is the rate at which energy is absorbed or produced within a circuit. A source of energy such as voltage will produce or deliver power while the connected load absorbs it. For example, light bulbs and heaters absorb electrical power and convert it into either heat, light, or both. The higher their value in watts the more electrical power they are likely to consume. If the power source does not carry enough electricity for the load to be powered, then adjustments must be made so that the load can be powered by the power source. In the case of the battery powered lightbulb, a battery with increased voltage will burn out the bulb rather quickly because there is too much energy present, whereas a significant lack of voltage will result in very little or no light produced.
Using Ohm's Law Triangle, one can determine if the current flowing through an object is proportional to the voltage across it, including the objects electrical resistance. By identify two of the given values, one can easily use the triangle to determine the missing value.
V- Voltage
I- Current
R- Resistance
Questions & Answers:
1) Determine how the concept of completing a circuit and creating a system of electricity can be applied and utilized in everyday life.
Answer: Answers will vary, but a basic understanding of electrical circuits and the flow of energy can help with determining problems with household items that appear to shut down or go out. By checking the terminals, ensuring appropriate input voltage, checking circuit breakers, and determining areas of resistance, one could relatively easily identify and fix common issues. On a grand scale, this knowledge could be used to design and create larger systems with circuits, breakers, and switches to direct and redirect the flow of electrons and electricity.
2) An electric heater draws 3.5 A from a 110 V source. Using Ohm's Law Triangle, determine what the resistance of the heating element is.
Answer: Resistance= Voltage/Current Resistance= 110/3.5 Resistance= Approximately 31
3) How can the concept of electricity flow be related to the human body?
Answer: Answers will vary. Your brain dispatches millions of electrical signals along the nerves of your central nervous system. These nerves connect with your muscles and provide the power to complete an action or movement. These electrical signals allow you to brush your teeth, eat a meal, and perform every day functions. If the circuit is open (impeded or incomplete) then your muscles will not react to the electrical impulses sent to them OR your muscles will receive nerve impulses that were not intended to be sent.
Applications to Everyday Life:
1. Circuits are found in most common electronics that people use, whether in the form of parallel and series circuits or a combination of the two. In a series circuit, energy flows in a direct pathway. If there is not a stable connection, then the following energy recipients will be compromised and unable to receive the energy needed to do work. A common example of this would be Christmas lights, as they are generally based on series circuits. When you test your lights before putting them up, one may notice that their lights light up to a certain portion of the strand, and sometimes simply replacing the blown out bulb with a new one will allow energy to flow through the entire circuit and light up your entire set of lights. In a parallel circuit, energy is passed through energy recipients, and the other recipients are able to receive and use the energy provided to them if one recipient is out. Computers, televisions, handheld electronics all utilize a series of parallel circuits.
2. Energy transformers utilize alternating current in order to change the voltage levels in a circuit. In the past, homes and businesses far away from a power plant were unable to receive electrical power.Carrying voltages across long distances through wires has a lot of resistance, meaning that a significant voltage of electricity must be carried through these power lines. Transformers allow that excessive amount of energy to be moderated into useable voltages of 220 or 110 for business or residential uses. Transformers conduct, alter, or modify electrical currents and transfer power through electromagnetic induction between circuits at the same frequency.
3. Cost. Understanding how electricity flows into the home and understanding how to open and close your electrical circuits will provide significant financial motivations. Leaving common household circuits open (lights, electronics turned on when not in use) will result in an increase of payment to the electrical company. In addition to paying more for energy that is not being utilized, there is an additional financial cost by having to replace the items that become worn out by the constant flow of energy through them (such as television sets, computer monitors, light bulbs, etc). Increased and prolonged usage of electronic devices decreases their shelf life and they will need to be replaced more frequently.
Photographs:
Both wires touching the screw thread contact OR the foot contact. This does not allow electrons to move in a circuit into and out of the light bulb, resulting in the electricity not able to flow through the light bulb and light it.
In these photographs, each wire is touching a different component of the lightbulb. It does not matter which component the positive or negative wires touch, but only that they do touch different components which allows electrons to freely flow through the load and back to the battery.
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