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

2 What is it?

3 The movement of electrons through a conductive material Electrons bump into other electrons in adjacent shells (called valence shells) and continue down the path

4 Electrons, which are negatively charged, emerge from the negative terminal of the power supply Conventional notation, however, is to refer to the electricity as emitting from the positive terminal of the power supply Electrons will only flow if there is a complete circuit for them to flow around

5 How you should be thinking about electric circuits: Voltage the “speed”, and subsequent force, that pushes the current through the circuit Water analogy The higher the water fall the more “voltage”

6 How you should be thinking about electric circuits: Resistance friction that impedes flow of current through the circuit Water analogy rocks in the river

7 How you should be thinking about electric circuits: Current The actual “substance” that is flowing through the wires of the circuit (electrons!) Water analogy The water molecules

8 UNDERSTANDING ELECTRICITY Air is conductive…if you have enough voltage to push the electrons through it (i.e. – lightening) 10,000 volts might not hut you…but if it pushes just 1 amp of current through your heart it can be fatal If the circuit has no resistance, it’s called a short circuit and infinite current will flow until the circuit fails (i.e. – melts or depletes)

9 Ohm’s Law V = I x R Georg Simon Ohm ( ) I = Current (Amperes) (amps) V = Voltage (Volts) R = Resistance (ohms)

10 Ohm’s Law V = I x R Georg Simon Ohm ( ) So more voltage will provide you more current And more resistance will provide you less current

11 Simple Circuits Series 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

12 ELECTRICAL CIRCUITS Measurements

13 Measuring current A A This is how we draw an ammeter in a circuit. SERIES CIRCUITPARALLEL CIRCUIT

14 Measuring current SERIES CIRCUIT PARALLEL CIRCUIT Current is the same at all points in the circuit. 2A Current is shared between the components 2A 1A

15 Fill in the missing ammeter readings. ? ? 4A 3A? ? 1A ? 3A 1A Measuring current

16 Measuring voltage V This is how we draw a voltmeter in a circuit. SERIES CIRCUITPARALLEL CIRCUIT V

17 3V Series Circuit Voltage is shared between the components 3V 6V Measuring voltage Like a train running through brick walls

18 Parallel Circuit Voltage is the same in all parts of the circuit. 3V Like two people under the same waterfall Measuring voltage

19 Review V V 6V 4A A A a)

20 V V 6V 4A A A A b) Review

21 Review Answers 3V 6V 4A 6V 4A 2A 4A a)b)