ELECTRICAL CIRCUITS All you need to be an inventor is a good imagination and a pile of junk. -Thomas Edison

Would This Work?

Would This Work?

Would This Work?

The Central Concept: Closed Circuit

Current: continuous flow of electric charges through a material High Current (low voltage) Low Current (high voltage)

Voltage- difference in electric potential between two points (push that causes electrons to move) Low Voltage High Voltage

Resistance: measure of how difficult it is for charges to flow through the objects

Simple Circuits Series circuit Parallel circuit All in a row 1 path for electricity 1 light goes out and the circuit is broken Parallel circuit Many paths for electricity 1 light goes out and the others stay on

circuit diagram Scientists usually draw electric circuits using symbols; Battery (cell) Light (resister) switch wires

Ohm’s Law Simple analogy: Water in a hose Electrons in a copper wire are analogous to water in a hose. Consider the pressure valve as the applied voltage and the size of the hose as the source of resistance. The absence of pressure in the hose, or voltage across the wire will result in a system without motion or reaction. A small diameter hose will limit the rate at which water will flow, just as a small diameter copper wire limits the flow of electrons. 3

Ohm’s Law Voltage = Current x Resistance Current (amps)= Voltage Georg Simon Ohm (1787-1854)

Ohm’s Law Current (amps)= Voltage Resistance the greater the voltage (or pressure) across a resistor, the more the current. The more the resistance, for the same voltage, the less the current. 4

1. How did adding more voltage affect the current (speed of motor)? Lab Questions: 1. How did adding more voltage affect the current (speed of motor)? 2. How did adding more resistance (lights + motor) affect the current (speed)?

PARALLEL CIRCUIT Place two bulbs in parallel. What do you notice about the brightness of the bulbs? Add a third light bulb in the circuit. What do you notice about the brightness of the bulbs? Remove the middle bulb from the circuit. What happened?

measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A

measuring current A A This is how we draw an ammeter in a circuit. PARALLEL CIRCUIT SERIES CIRCUIT

measuring voltage The ‘electrical push’ which the cell gives to the current is called the voltage. It is measured in volts (V) on a voltmeter V