Power rating, current and fuse choice: Class 10 practice

P = VI, so an appliance's current I = P/V. Read the method, follow the three worked examples, then try the six questions.

What you should know first

Electric power

The idea behind power rating, current and fuse choice

P = VI, so an appliance's current I = P/V. A fuse should be rated a little above the normal current. Resistance of the appliance is V²/P.

Step-by-step method

I = P/V.
R = V²/P.
Choose the next fuse rating above I.

Worked example 1 (Basic)

Find the current drawn by a 2000 W, 220 V appliance.

I = 2000/220
= 9.091 A
Answer: 9.091 A

Worked example 2 (Standard)

Find the resistance of a 60 W, 220 V bulb or heater when working.

R = V²/P = 48400/60
= 806.67 Ω
Answer: 806.67 Ω

Worked example 3 (Challenge)

Which fuse (1, 2, 3, 5, 10, 13, 15 A) suits a 1500 W, 220 V appliance?

I = 6.818 A
Next rating above: 10 A
Answer: 10 A

Common mistakes and misconceptions

Choosing a fuse below the working current
Using P = V/I

Practice questions

(Basic) Find the current drawn by a 1000 W, 220 V appliance.
(Basic) Find the current drawn by a 1500 W, 220 V appliance.
(Standard) Find the resistance of a 500 W, 220 V bulb or heater when working.
(Standard) Find the resistance of a 2200 W, 220 V bulb or heater when working.
(Challenge) Which fuse (1, 2, 3, 5, 10, 13, 15 A) suits a 60 W, 220 V appliance?
(Challenge) Which fuse (1, 2, 3, 5, 10, 13, 15 A) suits a 100 W, 220 V appliance?

Answer key with full working

Q1: I = 1000/220 → = 4.545 A → Answer: 4.545 A
Q2: I = 1500/220 → = 6.818 A → Answer: 6.818 A
Q3: R = V²/P = 48400/500 → = 96.8 Ω → Answer: 96.8 Ω
Q4: R = V²/P = 48400/2200 → = 22 Ω → Answer: 22 Ω
Q5: I = 0.273 A → Next rating above: 1 A → Answer: 1 A
Q6: I = 0.455 A → Next rating above: 1 A → Answer: 1 A

Syllabus note

This skill is listed under "Electricity" for Class 10 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.

Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.

Related practice and notes

Frequently asked questions

Which chapter is power rating, current and fuse choice in?

"Electricity", Class 10 Physics (NCERT/CBSE). Other boards may place it differently.

How were the answers checked?

Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.

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