The following 20 Multiple Choice Questions (MCQ) are based on
Chapter 4: Electricity: Magnetic and Heating Effects from the NCERT Class 8
Science textbook Curiosity. Each question has four options - select the
best answer and click to check.
Instructions: Read each question carefully. Choose the most
appropriate option from (a), (b), (c), or (d). Click
Show Answer to reveal the correct answer with explanation.
Multiple Choice Questions
1A compass needle near a current-carrying wire deflects because current produces:
(a) A magnetic effect
(b) Only light
(c) Only sound
(d) Gravity
(a) is correct
Electric current creates a magnetic field around the conductor.
2What happens to compass deflection when the direction of current is reversed?
(a) It never changes
(b) The compass becomes a battery
(c) Current stops permanently
(d) It reverses direction
(d) is correct
Reversing current reverses the direction of the magnetic field.
3An electromagnet is usually made by winding insulated wire around a:
(a) Plastic sheet
(b) Glass rod
(c) Soft iron core
(d) Wooden spoon only
(c) is correct
A current-carrying coil strongly magnetises the soft iron core.
4Why is an electromagnet called temporary?
(a) It is always weak
(b) Its magnetism can be switched on and off with current
(c) It contains no wire
(d) It works only once
(b) is correct
Opening the circuit removes most of the core's magnetism.
5Which change generally strengthens an electromagnet?
(a) Increasing the number of coil turns
(b) Opening the circuit
(c) Removing the current
(d) Replacing the iron core with air
(a) is correct
More turns carrying current produce a stronger combined magnetic field.
6A lifting electromagnet releases iron scrap when:
(a) The current increases
(b) More turns are added
(c) The core becomes iron
(d) The circuit is switched off
(d) is correct
Without current, the soft iron core loses its strong temporary magnetism.
7A current-carrying wire becomes hot due to the:
(a) Force of gravity
(b) Reflection of light
(c) Heating effect of electric current
(d) Cooling effect of magnetism
(c) is correct
Electrical energy is converted into thermal energy as current passes through resistance.
8Which appliance mainly uses the heating effect of current?
(a) Hand lens
(b) Electric iron
(c) Magnetic compass
(d) Permanent bar magnet
(b) is correct
An electric iron heats a resistive element to warm its soleplate.
9Why is nichrome used in heating elements?
(a) It produces substantial heat and tolerates high temperature
(b) It is an electrical insulator
(c) It melts at low temperature
(d) It cannot carry current
(a) is correct
Nichrome has relatively high resistance and remains stable when hot.
10For wires of the same material and thickness, which usually heats more for the same current and time?
(a) The shorter wire always
(b) Both cannot heat
(c) Length has no relation to resistance
(d) The longer wire
(d) is correct
A longer wire has greater resistance and converts more electrical energy to heat for fixed current.
11For equal-length nichrome wires, a thinner wire generally has:
(a) No heating effect
(b) Less resistance in every case
(c) Greater resistance
(d) Zero resistance
(c) is correct
Smaller cross-sectional area increases resistance.
12A fuse protects a circuit by:
(a) Acting as a permanent magnet
(b) Melting and breaking the circuit when current is excessive
(c) Increasing current indefinitely
(d) Storing electric charge
(b) is correct
The fuse wire heats and melts before excessive current can damage appliances or wiring.
13A cell converts mainly:
(a) Chemical energy into electrical energy
(b) Magnetic energy into mass
(c) Heat into matter
(d) Sound into gravity
(a) is correct
Chemical reactions between electrodes and electrolyte drive charge through the external circuit.
14In a simple lemon cell, lemon juice acts as the:
(a) Insulating core
(b) Switch only
(c) Electromagnet
(d) Electrolyte
(d) is correct
Its dissolved ions allow chemical reactions and internal charge transport.
15Why are two different metals used as electrodes in a simple voltaic cell?
(a) Only to change colour
(b) To stop reactions
(c) Their differing chemical behaviour creates a potential difference
(d) They must have the same chemical behaviour
(c) is correct
Different tendencies to participate in chemical reactions help drive electron flow.
16A dry cell is called 'dry' because its electrolyte is:
(a) Only air
(b) A moist paste rather than a freely flowing liquid
(c) Completely absent
(d) Pure metal
(b) is correct
The electrolyte is immobilised as a paste, making the cell portable.
17A battery consists of:
(a) One or more connected cells
(b) Only a switch
(c) A coil without a source
(d) A compass and nail
(a) is correct
Cells are combined to provide the required voltage or capacity.
18Which type of battery is designed to be used repeatedly after charging?
(a) Single-use dry cell only
(b) Lemon without electrodes
(c) Open circuit
(d) Rechargeable battery
(d) is correct
Charging drives reversible chemical changes so the battery can supply energy again.
19Why should used batteries go to authorised e-waste collection?
(a) They contain only water
(b) Recycling increases pollution
(c) They contain valuable and potentially harmful materials
(d) They are ordinary food waste
(c) is correct
Safe collection prevents toxic materials and fire hazards while recovering useful metals.
20If a coil still carries current after its iron core is removed, a nearby compass will:
(a) Lose its needle
(b) Still deflect, usually less strongly
(c) Never deflect
(d) Turn into an electromagnet
(b) is correct
The coil itself produces a magnetic field; the iron core mainly strengthens it.
