Electricity: Circuits and their Components MCQs (Class 7 Science, NCERT)

110 practice questions on Electricity: Circuits and their Components, a chapter in the NCERT Class 7 Science textbook. Every question includes a written explanation. Try the samples below - the answer stays hidden until you ask for it.

Sample questions

Q1
medium
The wires inside an electric plug are made of copper. What property of copper decides this choice?
  1. A It lets current pass through it easily
  2. B It is the lightest material that can be found
  3. C It stops current from passing, which makes the plug safe
  4. D It can be seen easily in the dark
Show answer and explanation

Correct answer: A - It lets current pass through it easily

Copper is a very good conductor, so current passes through it with little difficulty and reaches the appliance. A material that stopped the current would make the plug useless. Weight is not what decides the choice, and several materials are lighter. Being visible in the dark has nothing to do with carrying current.
Q2
medium
In a glowing bulb, why does only the thin filament light up while the thick wires holding it stay dull?
  1. A The thick wires are made of plastic and cannot carry current
  2. B The filament is far thinner, so it becomes hot enough to give out light
  3. C Current passes through the filament only and never through the thick wires
  4. D The glass cover stops the thick wires from being seen glowing
Show answer and explanation

Correct answer: B - The filament is far thinner, so it becomes hot enough to give out light

The same current passes through the thick wires and the filament, but the very thin filament heats up far more and reaches a temperature at which it glows. The thick wires are metal, not plastic, or no current could reach the filament at all. Since they are in the same path, they carry the same current. The glass is clear, so anything glowing inside would be seen.
Q3
easy
The thin coiled wire inside a bulb, which glows brightly when current passes, is called the
  1. A terminal
  2. B holder
  3. C filament
  4. D contact
Show answer and explanation

Correct answer: C - filament

The thin coiled wire inside the glass cover is the filament, and it is the part that becomes white hot and gives out light. A terminal belongs to a cell. The contacts are the metal parts at the base of the bulb. The holder is the fitting into which a bulb is screwed.
Q4
medium
Why is a bathroom a risky place to use an electrical appliance?
  1. A Bathrooms have less air, so appliances overheat
  2. B Appliances work faster in damp air and wear out
  3. C Water makes plastic coverings become conductors for ever
  4. D Wet skin and wet floors let current pass through the body easily
Show answer and explanation

Correct answer: D - Wet skin and wet floors let current pass through the body easily

Water on the skin and underfoot gives the current an easy route through the body to the ground, so any fault becomes far more dangerous there. The amount of air in a room does not decide whether an appliance overheats. A plastic covering stays an insulator; the danger comes from the water outside it. Damp air does not make an appliance run faster.
Q5
medium
Read these two statements about an ordinary electric wire. (i) Its outer covering is an insulator. (ii) The material inside the covering is a conductor. Which of them is correct?
  1. A Only (ii)
  2. B Only (i)
  3. C Neither (i) nor (ii)
  4. D Both (i) and (ii)
Show answer and explanation

Correct answer: D - Both (i) and (ii)

A wire is built from two materials doing opposite jobs: a metal core that carries the current and a plastic sleeve that blocks it, so both statements are correct. Choosing only one of them describes half the wire. Rejecting both would leave the wire unable either to carry current or to be handled safely.
Q6
easy
A simple tester for finding out whether a material conducts is made from
  1. A two bulbs joined by a single wire
  2. B a switch and a plastic board only
  3. C a cell, a bulb and two free wire ends
  4. D a cell joined to a wooden block
Show answer and explanation

Correct answer: C - a cell, a bulb and two free wire ends

A tester is just an incomplete circuit: a cell and a bulb with two loose wire ends waiting to be bridged by the material under test. Two bulbs with one wire form no complete loop and have no source. A switch on a board has neither a source nor a bulb to show a result. A cell joined to wood gives no signal to watch.

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