1. V

2. Ohm’s Law
The ratio of the potential difference to the current in a metal conductor is a constant. This is equal to the resistance.
R = V/I
R- resistance(Ω) I- current (Amps)
V- Potential difference (V)

3. EXAMPLE
What is the resistance of a lamp that is plugged into a 120V outlet and has a current of 0.75Amp?
R = V/I = 120V / 0.75Amp
R= 160Ω
b) What is the power of the bulb?
P=VI = 120V(0.75Amp)
P = 90 Watts

4. Power and Work W = Pt = VIt = I2Rt = V2 t R P=VI = (IR)I = I2R
P = V(V/R) = V2/R
W = Pt = VIt = I2Rt = V2 t R
*all on reference table

5. CIRCUIT SYMBOLS Resistor VariableResistor Switch Battery (DC Source)
Dry cell
Switch
Battery (DC Source)
Lamp
Generator (AC source)

6. MORE SYMBOLS Electrical ground Motor
Voltmeter- Measures drop in potential across a resistance. (Placed in parallel)
Ammeter- measures current in the circuit (placed in series)
Galvonometer- used to measure very small amounts of current.

7. SIMPLE CIRCUIT
*You could also use a resistance symbol for the lamp

8. When diagraming
Always label values for voltage, current and resistance.
Always show direction of current when a battery is in the circuit.
Make sure you use the correct symbols

9. Example
A circuit contains a 60V battery, an ammeter, a switch and a lamp of 30Ω. Draw a circuit diagram and determine the reading on the ammeter.
R=30Ω
R= V/I
30Ω = 60V / I
I = 2Amp
V=60V
I = 2 Amp