Electric Circuits Electric charges always move from high-voltage to low-voltage. Travels from negative to positive [ Click Here for an Interactive Example

Electric Circuits Voltage difference “forces” charges along a conductor and is measured in volts (V) Also called potential difference [

[ Water Tower analogy for Voltage

phttp:// Common Error About Voltage…

Electric Circuits Electric Current is the flow of charges (electrons) and is measured in amperes (A). [

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Electric Circuits Resistance is the tendency for materials to oppose the flow of electrons. Electrical energy is commonly changed into heat, light, or motion. [

Electric Circuits Resistance is measured in ohms (Ω). Click here for a video example of resistance. phttp://

Ohm’s Law As the resistance in the circuit increases, the current (number of charges) decreases. V = I R Click Here for an Interactive Example

Ohm’s Law Example: A circuit has a resistance of 0.5 Ω and has a current of 3.0 A. What size battery in volts is needed? V = (3.0 A) x (0.5 Ω) V = 1.5 V

Ohm’s Law Example: A 9-volt battery is used in a circuit with a resistance of 1.5 Ω. What current is needed? (9 V) = I (1.5 Ω) (1.5 Ω) I = 6.0 A

Circuit Diagrams A 2-dimensional representation of an electrical circuit. [

Some diagram symbols include… Open Switch Light Bulb Voltmeter Ammeter or

Series Circuits The current only has one possible circuit to pass through. [

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Parallel Circuits There are two or more branches on each circuit for current to move through. [

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Circuit Protection Devices If too much current flows through a circuit, a safety device shuts off the current in order to prevent it from overheating.

Circuit Protection Devices Fuses A small piece of metal that will melt if too much current passes through it. [

May only be used once, then must be replaced.

Circuit Protection Devices Circuit Breaker A piece of metal bends if too much current passes through, and it turns off the switch to the circuit. Just need to reset the switch to use again [