1. ⇒ (MHT CET 2023 9th May Evening Shift )

If the frequency of the input voltage is $50 Hz$ , applied to a (a) half wave rectifier and (b) full wave rectifier. The output frequency in both cases is respectively

A. $50 Hz, 50 Hz$

B. $50 Hz, 100 Hz$

C. $100 Hz, 100 Hz$

D. $100 Hz, 50 Hz$

Correct Option is (C)

The output frequency is doubled in a full wave rectifier, while there is no change in the case of a half wave rectifier.

2. ⇒ (MHT CET 2021 21th September Morning Shift )

In a pure silicon, number of electrons and holes per unit volume are $1.6 \times 10^{16} m^{- 3}$ . If silicon is doped with Boron in a way that on doping hole density increases to $4 \times 10^{22} m^{- 3}$ . Then electron density in doped semiconductor will be

A. $6.4 \times 10^{- 9} m^{- 3}$

B. $6.4 \times 10^{9} m^{- 3}$

C. $6.4 \times 10^{- 10} m^{- 3}$

D. $6.4 \times 10^{10} m^{- 3}$

Correct Option is (B)

$\begin{aligned} n_{i} = 1.6 \times 10^{16} m^{- 3}, n_{h} = 4 \times 10^{22} m^{- 3} \\ n_{e} n_{h} = n_{i}^{2} \\ ∴ n_{e} = \frac{n_{i}^{2}}{n_{h}} = \frac{{(1.6 \times 10^{16})}^{2}}{4 \times 10^{22}} = \frac{1.6 \times 1.6 \times 10^{32}}{4 \times 10^{22}} \\ = 6.4 \times 10^{9} m^{- 3} \end{aligned}$

3. ⇒ (MHT CET 2021 20th September Evening Shift )

A rectifier is used to

A. convert a.c. to d.c.

B. amplify a weak signal

C. generate intermittent voltage

D. convert d.c. to a.c.

Correct Option is (A)

Currently no explanation available

4. ⇒ (MHT CET 2021 20th September Morning Shift )

The frequency of a given a.c. signal is 'N' Hz. When it is connected to a half wave rectifier, the number of output pulses given by the rectifier in 1 second is

A. $\frac{N}{4}$

B. $\frac{N}{2}$

C. N

D. 2N

Correct Option is (C)

Frequency = N

For each wave, a positive pulse is given as output

Hence, N output pulses are given out.

⇒Semiconductor Devices