Coulomb of charge (electrons) Think of it as a “bag of electrons” (containing electrons!) ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺

Current The number of Coulombs flowing past a point in the circuit every second. I = Q/t ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ A I’m counting how many coulombs of electrons go past me every second 1 Amp = 1 coulomb per second

In a series circuit Current is the same at any point in the circuit 2.5 A

In a parallel circuit The current splits (total current stays the same) 2.5 A 1.25 A

Voltage(emf) ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ V I’m checking the difference in energy (per coulomb) between the 2 red arrows 1 Volt = 1 Joule per coulomb

Voltage (p.d.) ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ V I’m checking the difference in energy (per coulomb) before and after the lamp 1 Volt = 1 Joule per coulomb

In a series circuit The sum of the voltages across the lamps equals the voltage across the cells 9 V 3 V

In a parallel circuit In a simple parallel circuit, voltage across each lamp equals the voltage across the cells 5 V

Resistance Measures how difficult it is for current to flow. Measured in Ohms (Ω) VA Resistance = voltage/currentR = V/I

Resistance of a lamp AV Resistance = voltage/currentR = V/I Vary the voltage and current using a variable resistor (rheostat). Plot a graph of resistance against current

Resistance of a lamp V(V)I(A)R(Ω) I(A) R(Ω)

Resistance of a lamp As the current in a lamp increases, it gets hotter, and its resistance increases. Why?

Ohm’s Law V = IR V R I X

Power The amount of energy used by a device per second, measured in Watts (Joules per second) VA Power = voltage x currentP = VI

Power The amount of energy used by a device per second, measured in Watts (Joules per second) VA Power = voltage x currentP = VI ☺ Can you copy this please?

Example A 200 W television is plugged into the 110V mains. What is the current in the television? P I V X

Example A 200 W television is plugged into the 110V mains. What is the current in the television? I = P/V = 200/110 = 1.8A P I V X

Example A kettle uses 240V and 8A. What is its power? P I V X

Example A kettle uses 240V and 8A. What is its power? P = VI = 240x8 = 1920W (=1.9kW) P I V X

Electric symbols

Cell and battery of cells

Lamp

Switch

Ammeter

Voltmeter

Resistor

Variable resistor (rheostat)

Thermistor Resistance decreases with increasing temperature Temp Resistance

Light-dependent resistor (LDR) High resistance in the dark but a low resistance in light

Diode Allows current to flow in one direction only (from + to – in the direction of the “arrow)

Captain Jack Sparrow smoking a cigar

Two cowboys on a tandem

Two fried eggs in a frying pan

3 wizards looking down a well

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