Ohm’s law: find current and resistance — Electronics for kids

Remember

Cover what you want — “cover I in the triangle to get V ÷ R; cover R to get V ÷ I”

1. I = V ÷ R (amperes = volts ÷ ohms).
2. R = V ÷ I (ohms = volts ÷ amperes); use amperes, not mA, in the formula.
3. Example: 5 V and 25 mA (0.025 A) → R = 5 ÷ 0.025 = 200 Ω.

Use it for: Physics problems on Ohm’s law, choosing a resistor and checking how much current a part takes.

Worked example: 🔺 A 6 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? → 0.5

✏️ Practice

Work it out in your head or on paper, then tap your answer — or type it and press Check. Stuck? Press “Show me how”.

🏁 Lesson 13 test

20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.

🏅 Sign in with Google to earn the 🧮 Current Calculator badge when you pass — and a certificate when you finish all 10 lessons of Part 2 · Components and Ohm’s law. You can still take the test without signing in.

🖨️ Electronics Worksheet: Ohm’s Law – Current and Resistance

• Worksheet set 1 (PDF)
• Worksheet set 2 (PDF)
• Worksheet set 3 (PDF)