Electricity/Electronics

Summary of Chapter 1:

The electric current is a measure of how much electricity is flowing in a wire, and is expressed in Amperes (Amp or I).

The voltage is the measure of the electric pressure exerted into a wire or circuit by a battery or other power source, and is expressed in volts. Using Ohm's Law, voltage equals current multiplied by resistance (V = I x R).

Switches are used to turn on or off the flow of electricity in a circuit.

A light bulb converts electricity into light.

Most electronic products have components mounted on circuit boards with wires literally printed on the board surface.

Electrical circuits are all combinations of series and parallel configurations.

A short circuit is a no-resistance path across a power source and causes damage to components and batteries.

Solder is a special metal that is melted to make solid electrical connections.

Schematics are engineering drawings of circuits using symbols.

Summary of Chapter 2:

An electric current flowing in a wire has a magnetic field.

A generator uses mechanical motion to create electricity and a motor uses electricity to create mechanical motion.

A fuse is a special wire that breaks when an excessively high current flows through it. A fuse is used for safety.

Electrical outlets are 120v, and can supply enough current to kill people.

Static electricity can cause clothes to stick together. Lighting occurs when static electricity in clouds discharges into the ground.

Only a small amount of the electricity used by lightbulbs is converted into light, the rest becomes heat, remember the law of energy conversion.

Summary of Chapter 3:

Resistors are used to limit and control the current in a circuit.

Resistance is a measure of how much something opposes the flow of electricity in a circuit, and is expressed in ohms. Using Ohms Law, Resistance equals voltage divided by current (R = V / I).

Light emitting diodes (LEDS) are one way low current light bulbs. They have a turn-on threshold of about 1.5 volts. A resistor should always be placed in series with a LED.

Placing resistors in series increased the total resistance. Placing resistors in parallel decreases the total resistance.

In a circuit, the current equals the voltage divided by the resistance (I =V/R). This is know as Ohms Law.

Power measured how much energy is moving through a circuit, it equals the voltage multiplied by the current and is expressed as Watts (W=I x V).

Materials which have a very low resistance are called conductors. Materials which have very high values of resistance are called insulators.

Photoresistors change their resistance value when light shines on them.

All circuits flow through resistors which produce heat in them.

OR, AND, NOR, NAND, and NOT circuits are basic building blocks of computers.

Digital electronics uses numbers to represent an electronic signal. The accuracy of the digital representation depends on how accurately and how often the original signal is measured.

Computers store numbers using arrays of transistors that are switched on and off.

Summary of Chapter 4:

Capacitors are components that can store electricity for periods of time.

Capacitance measures how much electrical charge may be stored in a capacitor, and is usually expressed in microfarads,

Capacitors block slow changing voltages and pass fast changing ones.

Capacitor charge/discharge times are proportional to the resistance and capacitance in the charge/discharge paths.

Placing capacitors in series reduces the capacitance, and placing capacitors in parallel increases the capacitance.

Summary of Chapter 5:

The resistance of semiconductors may be controlled by their operating conditions.

Semiconductors have a turn-on level (0.7V for silicon), after which the resistance becomes very low in one direction.

Transistors have three connection points, called the emitter, base, and collector.

The transistor is a current amplifier, it uses a small amount of current to control a large amount of current.

When a small current flows into the base and out of the emitter in a NPN transistor, a larger current flows into the collector and out the emitter. In a PNP transistor, current flows into the emitter and out of the base and collector.

A microphone is a resistor that changes when exposed to sound. This change in resistance will change the current through a circuit when sound waves apply pressure to its surface.

Summary of Chapter 6:

A speaker uses a changing electrical signal to make variations in air pressure.

All sounds are variations in air pressure that your ears hear.

Oscillators use feedback to set and control the frequency.

Frequency measures how fast something occurs, and is expressed in Hertz.

Audio refers to the range of frequencies that can be heard by human ears.

The whistle chip acts like a capacitor but can also make sound like a speaker does.

Capacitors have higher resistance at lower frequencies but lower resistance at higher frequencies.

Summary of Chapter 7:

Integrated circuits (IC) are miniature circuits with many transistors, resistors, capacitors and wires wall made on a semi conductive base.

The ICs in Snap circuits are modules containing specialized integrated circuits and supporting parts that are always needed with them.