Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.  
Assertion A: Diffusion current in a p-n junction is greater than the drift current in magnitude if the junction is forward biased.  
Reason R: Diffusion current in a p-n junction is from the n-side to the p-side if the junction is forward biased.  
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is NOT the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Answer 1

The Correct Option is C

To solve this question, let's analyze both the assertion and the reason:

Assertion (A):

The assertion states that the diffusion current in a p-n junction is greater than the drift current in magnitude if the junction is forward biased.

• In a forward-biased p-n junction, the potential barrier is reduced, allowing more majority carriers to cross the junction, resulting in an increase in the diffusion current.
• The diffusion current, which is due to the movement of charge carriers (electrons and holes) from high concentration to low concentration, dominates in a forward-biased junction.
• Hence, the diffusion current is indeed greater than the drift current, which occurs due to the electric field within the depletion region, when the junction is forward biased.

Therefore, Assertion (A) is correct.

Reason (R):

The reason suggests that the diffusion current in a p-n junction is from the n-side to the p-side if the junction is forward biased.

• In a p-n junction, under forward bias, the diffusion current direction is determined by the movement of carriers.
• Electrons move from the n-side to the p-side and holes move from the p-side to the n-side. However, the explanation must consider all carriers, not just one type.

The statement that the diffusion current is from the n-side to the p-side is incomplete and misleading because it only considers the electrons and ignores the overall movement of charge, which includes hole movement as well.

Thus, Reason (R) is not correct.

Conclusion:

After evaluating both statements, we conclude that Assertion (A) is correct, but Reason (R) is not correct. Therefore, the correct answer is:

A is correct but R is not correct