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Class 10 Science: Magnetic Effects of Electric Current, 8 practice questions with answers

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These are 8 practice questions on NCERT Class 10 Science Chapter 12, Magnetic Effects of Electric Current, each with a short answer, the units, and the textbook page it comes from. They cover magnetic field lines, the fuse and overloading, the wires and ratings of a domestic circuit, and numericals on the current an appliance draws. Try each one before you read the answer.

These questions are our own, drafted with AI help. Every number was re-computed by a test script and every statement was checked against the chapter, but no practising teacher has reviewed them yet. If you find a mistake, please tell us.

Magnetic field lines

Question 1. Assertion (A): Two magnetic field lines never cross each other. Reason (R): If they crossed, a compass needle at that point would point in two directions at once, which is impossible. Choose the correct option: both true and R explains A; both true but R does not explain A; A true and R false; or A false and R true.

Answer: A and R are both true, and R explains A. No two field lines are found to cross each other; if they did, the compass needle would point towards two directions at the point of intersection, which is not possible. (Section 12.1, page 197.)

Fuse, overloading and domestic circuits

Question 2. What protects a household circuit and its appliances from damage due to overloading? (A bulb; a fuse; or a switch.)

Answer: a fuse. A fuse in a circuit prevents damage to the appliances and the circuit due to overloading. The Joule heating in the fuse melts it and breaks the circuit when an unduly high current flows. (Section 12.4, page 205.)

Question 3. In a home, which wire usually has red insulation, which has black, and what is the potential difference between them in our country?

Answer: The wire with red insulation is the live wire (positive) and the one with black insulation is the neutral wire (negative). The potential difference between them is 220 V. (Page 204.)

Question 4. Why is the metallic body of an appliance such as a toaster or refrigerator connected to the earth wire?

Answer: The earth wire, with green insulation, provides a low-resistance conducting path for the current. If current leaks to the metallic body, its potential stays the same as that of the earth, so the user does not get a severe electric shock. (Page 204.)

Question 5. Why are the appliances in a house connected in parallel across the live and neutral wires?

Answer: So that each appliance has the same potential difference, and each has its own switch to turn the current through it on or off. (Page 205.)

Numericals on the current an appliance draws

Use P = VI (Chapter 11, "Electricity", page 191): the current is I = P ÷ V, and 1 kW h = 1 unit.

Question 6. A 1,100 W electric heater runs on the 220 V household supply. What current does it draw, in amperes?

Answer: 5 A. P = VI, so I = P ÷ V = 1,100 ÷ 220 = 5 A. A fuse rated below 5 A on this circuit would melt.

Question 7. A toaster of 880 W and a kettle of 1,320 W work together on a 220 V kitchen circuit. (a) What current does each draw? (b) What total current flows, and what must the circuit's fuse allow? (c) If both are used for 30 minutes every day for 30 days, how many units (kW h) of electricity do they use?

Answer: (a) Toaster: 880 ÷ 220 = 4 A; kettle: 1,320 ÷ 220 = 6 A. Each gets 220 V because they are in parallel (page 205). (b) The total is 4 + 6 = 10 A, so the fuse must allow more than 10 A. (c) The power is 880 + 1,320 = 2,200 W = 2.2 kW. In 30 days of 0.5 hour that is 15 hours, so 2.2 × 15 = 33 kW h, that is 33 units.

Question 8. A geyser of 3 kW works on 220 V. How much current does it draw, to two decimal places, and which of the two common domestic circuits (5 A or 15 A) should it be connected to?

Answer: I = P ÷ V = 3,000 ÷ 220 ≈ 13.64 A. That is more than 5 A, so it needs the 15 A circuit. The textbook says that often two separate circuits are used, one of 15 A rating for appliances with higher power ratings such as geysers and air coolers, and the other of 5 A rating for bulbs and fans. (Page 204.)

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Sources

All opened and read on 21 October 2026. Page numbers are the printed page numbers of the textbook.

The facts are from the textbook pages above. The questions, worked answers and checks are our own, and every number was re-computed by script. This guide is general information; follow your teacher and the textbook.