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Ohm's law explained for the electrical exam
Every calculation on the exam leans on Ohm's law. Lesson 2.1 covers it start to finish. Here's the quick version.
The breakdown, in plain English
- E = I × R. Voltage equals current times resistance.
- I = E ÷ R and R = E ÷ I are the same formula rearranged.
- Power: P = E × I. Watts equal volts times amps.
- Combine them: P = I² × R and P = E² ÷ R.
- Use the circle or wheel trick: cover what you're solving for, and the other two tell you whether to multiply or divide.
Worked example
Example: a 1,500 W heater on 120 V
- I = P ÷ E = 1,500 ÷ 120 = 12.5 amps.
- R = E ÷ I = 120 ÷ 12.5 = 9.6 ohms.
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