Question

Which of the following methods results in charging an object opposite to the charge on the charging body?
A) Charging by friction
B) Charging by contact
C) Charging by induction
D) Both A and C

Answer 1

Hint: Various methods of charging are implemented to charge uncharged bodies. Some of them make the charged body similarly charged and others make the charged body oppositely charged. Similarly charged simply means the same nature of charge, that is either positive or negative. Oppositely charged means, among two bodies, one is positively and the other is negatively charged.

Complete step by step answer:
There are three primary methods of charging uncharged bodies. These are charging by friction, charging by conduction/contact and charging by induction. Let’s discuss these methods and their differences, to solve the question.

Charging by friction involves rubbing two uncharged bodies with one another. In this process electron transfer takes place from one body to the other, that is from a body where electrons are loosely bound to the other body where electrons are strongly bound. Thus when charging by friction two neutral bodies are charged by equal and opposite amounts, one positive and one negative.

When we charge by contact, a charged body is used to conduct electrons from a relatively negatively charged body to a relatively positively charged body when contacted with one another. Thus in this charging the nature of the charged body is similar to the nature of the charging body. A positive charging body results in a positive charged body and a negative charging body results in a negative charged body.

In charging by induction, an uncharged body is charged opposite to the inducer, when placed in its close proximity. A positively charged inducer induces accumulation of negative charges on the nearer surface of the body to be charged and when the inducer is removed from the proximity, the uncharged body shows negative nature.

Thus we can conclude that charging by conduction produces a charged body of like nature and charging by friction and induction result in oppositely-charged charged bodies.

Therefore, the correct answer is (D), both (A) and (C).

Note: These are theoretical questions. There aren’t any quick tricks to solve these questions. The primary idea is to study and understand the methods of charging. Quick notes on methods of charging:
By friction, both charging and charged bodies are charged by equal and opposite amount, by contact or conduction, charging body and charged body have the same nature of charge, but the charge on the charged body is relatively less than the charging body.
In charging by induction, the charged body is oppositely charged and the magnitude of induced charge may be lesser than or equal to the magnitude of inducing charge.