Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : $$n - p - n$$ transistor permits more current than a $$p - n - p$$ transistor.
Reason R : Electrons have greater mobility as a charge carrier.

We need to evaluate both the Assertion and the Reason about transistors.

Assertion A: An $$n-p-n$$ transistor permits more current than a $$p-n-p$$ transistor.

Analysis of Assertion A:

In an $$n-p-n$$ transistor, the majority charge carriers are electrons, while in a $$p-n-p$$ transistor, the majority charge carriers are holes.

Since the mobility of electrons is greater than the mobility of holes, the $$n-p-n$$ transistor allows more current to flow for the same applied voltage.

Therefore, Assertion A is true.

Reason R: Electrons have greater mobility as a charge carrier.

Analysis of Reason R:

This is a well-known fact. In semiconductors, the mobility of electrons ($$\mu_e$$) is greater than the mobility of holes ($$\mu_h$$).

Therefore, Reason R is true.

Is R the correct explanation of A?

Yes. The reason the $$n-p-n$$ transistor permits more current is precisely because electrons (the charge carriers in $$n-p-n$$) have higher mobility than holes (the charge carriers in $$p-n-p$$). So Reason R directly explains Assertion A.

Hence, the correct answer is Option A: Both A and R are true, and R is the correct explanation of A.