Electricity: Magnetic and Heating Effects Mcq's Class 8

Q1. Which scientist first observed the magnetic effect of electric current?

a) Michael Faraday

b) Hans Christian Oersted(Correct)

c) Thomas Edison

d) James Watt

Explanation: In 1820, H.C. Oersted discovered that a compass needle deflects when kept near a wire carrying electric current.

Q2. The heating element of an electric iron is made up of:

a) Nichrome(Correct)

b) Copper

c) Aluminium

d) Iron

Explanation: Nichrome (an alloy of nickel and chromium) has high resistance and a high melting point, making it ideal for heating appliances.

Q3. A safety device based on the heating effect of electric current is called a:

a) Switch

b) Compass

c) Fuse(Correct)

d) Battery

Explanation: An electric fuse contains a wire with a low melting point that breaks the circuit by melting down if excessive current flows through it.

Q4. Which of the following increases the strength of an electromagnet?

a) Decreasing the current

b) Reducing the number of turns in the coil

c) Removing the iron core

d) Increasing the number of turns in the coil(Correct)

Explanation: The strength of an electromagnet depends directly on the amount of current passing through it and the number of turns wrapped in its coil.

Q5. The core material best suited for making a temporary electromagnet is:

a) Steel

b) Soft iron(Correct)

c) Copper

d) Nickel

Explanation: Soft iron magnetizes quickly when current flows and loses its magnetism almost instantly when the current is turned off.

Q6. Filament lamps work on which effect of electric current?

a) Heating effect(Correct)

b) Magnetic effect

c) Chemical effect

d) Shock effect

Explanation: The thin tungsten filament glows white-hot due to high resistance when electricity passes through it.

Q7. What device has replaced conventional electric fuses in modern household wiring layouts?

a) LED

b) Generator

c) MCB (Miniature Circuit Breaker)(Correct)

d) Transformer

Explanation: MCBs automatically trip off when current exceeds safe limits. They can easily be reset without replacing wires.

Q8. An electric bell makes use of an:

a) Electric fuse

b) Electromagnet(Correct)

c) LED bulb

d) Permanent magnet

Explanation: Electric bells utilize an electromagnet to continuously pull an armature strip, making a hammer strike a metallic gong.

Q9. The amount of heat produced in a wire depends on its:

a) Material only

b) Length and thickness only

c) Material, length, and thickness(Correct)

d) Current color coating

Explanation: Heat generation varies according to electrical resistance, which is determined collectively by the wire’s raw material, length, and cross-sectional area.

Q10. When electric current passes through a straight wire, the shape of the magnetic field lines around it are:

a) Concentric circles(Correct)

b) Straight lines parallel to wire

c) Parabolic paths

d) Ellipses crossing each other

Explanation: Current flowing along a line forms circular concentric magnetic field loops wrapped symmetrically all along the wire perimeter.

Quiz – Electricity: Magnetic and Heating Effects – Class 8