question_answer

                A n-p-n transistor conducts when:                                                                                                          

A)                 collector is positive and emitter is at same potential as the base

B)                 both collector and emitter are negative with respect to the base

C)                 both collector and emitter are positive with respect to the base

D)                 collector is positive and emitter is negative with respect to the base

Correct Answer: D

Solution :

                For amplifying action of a transistor, emittor-base junction is forward biased while base-collector junction is reverse biased. For forward biasing of emittor-base junction in n-p-n transistor, left n-side i.e. emittor should be connected to negative terminal and p-side (base) should be connected to positive terminal of the battery. On the other hand in right side, n-side (collector) should be connected to positive terminal of the battery to make base-collector junction reverse biased. The whole situation is shown in the figure for n-p-n transistor                 \[E\to Emitter\]                 \[B\to Base\]                 \[C\to Collector\]