Q: The typical operating current for a lightemitting diode is approximately:

5 to $ 20 m A $. A standard light-emitting diode is normally operated at a modest current so it emits light without being damaged. The common range is about 5 to 20 mA, which matches typical indicator LED specifications.

Q: In a semiconductor, which of the following statement is correct?

$ p-n $ junction is electrically neutral. In a p-n junction, the uncovered ionized donors and acceptors in the depletion region create equal and opposite charges, so the junction as a whole is electrically neutral. The other options are incorrect because Si is not superconducting at 0 K, acceptor levels are near the valence band, and donor atoms contribute electrons, not holes.

Q: For a common emitter amplifier, current gain is $ 60 . $ If the emitter current is $ 6.6 ~ m A $ the collector current is :

6.492 m $ A $. In a common-emitter transistor, current gain is typically $\beta = I_C/I_B$. With $\beta = 60$, the base current is $I_B = I_C/60$, and since $I_E = I_C + I_B$, the collector current is slightly less than the emitter current. That gives $I_C = 6.492\,\text{mA}$.

Q: If the input frequency of a full wave rectifier is $ 50 H z $ ac. Its output frequency is

$ 100 H z $ pulsating do. In a full-wave rectifier, both the positive and negative half-cycles are converted into positive output pulses. That doubles the ripple frequency, so a 50 Hz input becomes 100 Hz at the output.

Question 1

The typical operating current for a lightemitting diode is approximately:

Accepted Answer

5 to $ 20 m A $. A standard light-emitting diode is normally operated at a modest current so it emits light without being damaged. The common range is about 5 to 20 mA, which matches typical indicator LED specifications.

Question 2

In a semiconductor, which of the following statement is correct?

Accepted Answer

$ p-n $ junction is electrically neutral. In a p-n junction, the uncovered ionized donors and acceptors in the depletion region create equal and opposite charges, so the junction as a whole is electrically neutral. The other options are incorrect because Si is not superconducting at 0 K, acceptor levels are near the valence band, and donor atoms contribute electrons, not holes.

Question 3

For a common emitter amplifier, current gain is $ 60 . $ If the emitter current is $ 6.6 ~ m A $ the collector current is :

Accepted Answer

6.492 m $ A $. In a common-emitter transistor, current gain is typically $\beta = I_C/I_B$. With $\beta = 60$, the base current is $I_B = I_C/60$, and since $I_E = I_C + I_B$, the collector current is slightly less than the emitter current. That gives $I_C = 6.492\,\text{mA}$.

Question 4

If the input frequency of a full wave rectifier is $ 50 H z $ ac. Its output frequency is

Accepted Answer

$ 100 H z $ pulsating do. In a full-wave rectifier, both the positive and negative half-cycles are converted into positive output pulses. That doubles the ripple frequency, so a 50 Hz input becomes 100 Hz at the output.

NEET Physics: Electronics questions with solutions

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