Ohm’s Law
Voltage equals current times resistance.
V = IR
1What it means
Ohm’s law is the backbone of circuit analysis: for a fixed resistance, more voltage drives more current. Units: volts (V), amperes (A), ohms (Ω).
2Variables
| Symbol | Meaning |
|---|---|
| V | Voltage / potential difference (V) |
| I | Current (amperes, A) |
| R | Resistance (ohms, Ω) |
3Worked examples
Example 1 Worked solution
Q. A 12 V battery drives 0.5 A through a resistor. Find R.
- V = IR ⇒ R = V / I.
- = 12 / 0.5.
✓ R = 24 Ω
4Where it's used
- ✦Designing and analysing electric circuits.
- ✦Choosing the right resistor for a current.
5Tips & common mistakes
- !Rearrange as I = V/R or R = V/I as needed.
- !Electrical power is P = VI = I²R.