Physics · Heat, sound and electricity
Electric Circuits and Ohm's Law
Ohm's law tells us how much current flows when a voltage is applied across a resistance.
- Total resistance
- 12 Ω
- Total current I = V ÷ R
- 0.5 A
- Voltage across R₁ / R₂
- 2 V / 4 V
- Current in R₁ / R₂
- 0.5 A / 0.5 A
- Power P = V × I
- 3 W
Connection
Try this
- Double the voltage. What happens to the current?
- Compare the total resistance in series and parallel.
- In parallel, which resistor carries more current?
Key ideas
- V = I × R
- Series: R = R₁ + R₂ (same current through each).
- Parallel: 1/R = 1/R₁ + 1/R₂ (same voltage across each).