CBSE Class 12 · 2008 · All India · SemiconductorsShort Answer

In only one of the two circuits shown, the lamp L glows. State, with reason, in which circuit the lamp lights up.

Solution

For transistor action the emitter-base junction must be forward biased and the collector-base junction reverse biased.
In circuit (i) the emitter-base junction is not forward biased, so negligible current flows and the lamp L does not light.
In circuit (ii) the emitter-base junction is forward biased, so a collector current flows through L and the lamp lights up.

Lamp glows in circuit (ii).

CBSE Class 12 Board · 2008 · All India · Subjective

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