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General ScienceEasyAsked in: NDA · NDA-I 2019, GAT

Which one of the following can charge an insulator?

  1. A.Current electricity
  2. B.Static electricity
  3. C.Magnetic field
  4. D.Gravitational field

Correct answer

B. Static electricity

Explanation

The correct answer is B, Static electricity. An insulator is charged by friction: rubbing transfers electrons from one surface to another, and because electrons cannot move through an insulator, the charge stays where it is as static electricity.

When a plastic comb is rubbed on dry hair or a glass rod is rubbed with silk, one body loses electrons and becomes positive while the other gains them and becomes negative. In an insulator this charge stays at rest on the surface, which is why a charged comb can pick up bits of paper. This is the principle behind the electrophorus and the Van de Graaff generator, and it is also why sparks sometimes jump when you touch a door handle after walking on a carpet.

A is wrong because current electricity is a flow of charge, which needs a conductor; it cannot flow through an insulator to charge it.

C is wrong because a magnetic field does not put any net charge on a body at rest.

D is wrong because gravity acts on mass and has no effect on electric charge.

Exam tip: insulators are charged by rubbing (friction); conductors can also be charged by induction.

Practice Questions

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Q1.General ScienceAsked in: UPSC Civil Services · CSE Prelims 2022, GS Paper IMedium

Which of the following are nitrogen-fixing plants?

1. Alfalfa

2. Amaranth

3. Chickpea

4. Clover

5. Purslane (Kulfa)

6. Spinach

Select the correct answer using the code given below:

  1. A.1, 3 and 4 only
  2. B.1, 3, 5 and 6 only
  3. C.2, 4, 5 and 6 only
  4. D.1, 2, 4, 5 and 6
Show answer
Correct answer: A. 1, 3 and 4 only

Alfalfa, chickpea and clover are legumes, and legumes fix nitrogen. Plants of the legume family (Fabaceae) carry root nodules that house Rhizobium bacteria.

Q2.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

The mass number of an element is NOT changed when it emits

  1. A.Alpha and Beta radiations only
  2. B.Alpha and Gamma radiations only
  3. C.Beta and Gamma radiations only
  4. D.Alpha, Beta and Gamma radiations
Show answer
Correct answer: C. Beta and Gamma radiations only

Neither beta nor gamma emission changes the total number of protons and neutrons in a nucleus, so the mass number stays the same.

Q3.General ScienceAsked in: UPSC CAPF · CAPF 2025, Paper IMedium

Which one among the following statements about facilitated transport in plants is correct?

  1. A.All passive transports are types of facilitated transport.
  2. B.Facilitated transport is an example of active transport.
  3. C.Water moves across plasma membrane by active transport.
  4. D.Facilitated transport requires assistance of carrier proteins.
Show answer
Correct answer: D. Facilitated transport requires assistance of carrier proteins.

In facilitated transport, molecules cross the membrane with the help of membrane proteins, while still moving down their concentration gradient.

Q4.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

Who among the following has coined the term 'Quark', the fundamental particles that make up protons and neutrons in an atomic nucleus ?

  1. A.Richard Feynman
  2. B.Murray Gell-Mann
  3. C.Albert Einstein
  4. D.Niels Bohr
Show answer
Correct answer: B. Murray Gell-Mann

The American physicist Murray Gell-Mann proposed quarks in 1964 and gave them their name. Gell-Mann, and independently George Zweig, suggested that protons, neutrons and other such particles are built from smaller units.