Question

In a transistor circuit, if emitter and collector connections are interchanged then

• A. emitter current will increase.
• B. base current decreases.
• C. collector current increases.
• D. no current flows in the circuit.

Hint:

Interchanging emitter and collector in a BJT reduces current gain and efficiency, leading to decreased base and collector currents.

Answer 1

The Correct Option is B

Step 1: Understand the role of emitter and collector in a transistor.
In a bipolar junction transistor (BJT), the emitter is heavily doped to supply charge carriers, while the collector is moderately doped and designed to collect carriers. The base is thin and lightly doped.
Step 2: What happens if emitter and collector are interchanged?
If you interchange the emitter and collector:
The new "emitter" (original collector) is not as heavily doped, so it cannot supply as many charge carriers.
The current gain ($\beta$) of the transistor drops drastically.
As a result, the base current increases for the same input, but the collector and emitter currents decrease.
Step 3: Analyze the options.
% Option (1) Emitter current will increase: Incorrect. Emitter current actually decreases.
% Option (2) Base current decreases: Correct. The base current decreases because the transistor's current gain drops.
% Option (3) Collector current increases: Incorrect. Collector current decreases.
% Option (4) No current flows in the circuit: Incorrect. Some current still flows, but much less efficiently. Final Answer: \[ \boxed{\text{base current decreases.}} \]