Question

Assertion: There is no current in the metals in the absence of electric fields.
Reason: Motion of free electrons are random.
A) Both assertion and reason are correct and the reason is the correct explanation for the assertion.
B) Both assertion and reason are correct but the reason is not the correct explanation for the assertion.
C) Assertion is correct but reason is incorrect.
D) Assertion is incorrect but reason is correct.

Answer 1

Hint: In order to be able to solve this question one must be aware of the concept of the electric current. An electric current is defined as a flow or stream of charged particles such as electrons or ions through an electrical conductor.

Complete answer:
The statement of assertion is “There is no current in the metals in the absence of electric fields.” This statement is absolutely correct because without an electric field a conductor will not produce current on its own. The electrons within the metal move in a haphazard way. However, a haphazard motion can not contribute to the current.

A current requires a stream of electrons, this is only possible under the influence of an electric field. Because an electric field provides drift velocity to free electrons which ultimately results in the current.

The statement of reason is “Motion of free electrons are random.”. This statement is also correct. As stated earlier the free electrons in a metal move in a haphazard manner. This also explains why there is no current in the metals in the absence of an electric field.

From the above discussion, it is clear that both the assertion as well as the reason are correct. Also, the reason perfectly provides an explanation for the given assertion.

Hence, option A is the correct answer.

Note: The following points regarding the concept of current must be remembered.
1. A continuous flow of electrons is current.
2. Metals have a large number of free electrons and hence they conduct more current.
3. Non-metals do not have a large number of electrons and hence they are bad conductors.
4. All non-metals except graphite are bad conductors of electricity.
5. The unit of current is coulomb per second (C/s) or ampere (A).