# Power Electronics MCQs Part 4

Power Electronics MCQs Part 4

## The Thyristor (SCR) is a

The Thyristor (SCR) is a

1. P-N-P device
2. N-P-N device
3. P-N-P-N device
4. None of these

Explanation: A Silicon-Controlled Rectifier, or SCR, is essentially a Shockley diode with an extra terminal added. This extra terminal is called the gate, and it is used to trigger the device into conduction (latch it) by the application of a small voltage. The figure below displays physical diagram and schematic symbol of SCR.

## A power transistor is a

A power transistor is a

1. Three terminal, bipolar, current controlled device
2. Three terminal, unipolar, voltage controlled device
3. Two terminal, bipolar, voltage controlled device
4. Two terminal, unipolar, current controlled device

Correct Answer: 1. Three terminal, bipolar, current controlled device

## The ratio of collector current to base current in a transistor is known as

The ratio of collector current to base current in a transistor is known as:

1. Alpha
2. Beta
3. Gamma
4. Zeta

Explanation:

The ratio of collector current to base current, β is the fundamental parameter characterizing the amplifying ability of a bipolar transistor. β is usually assumed to be a constant figure in circuit calculations, but unfortunately this is far from true in practice. As such, manufacturers provide a set of β (or “hfe”) figures for a given transistor over a wide range of operating conditions, usually in the form of maximum/minimum/typical ratings. It may surprise you to see just how widely β can be expected to vary within normal operating limits. One popular small-signal transistor, the 2N3903, is advertised as having a β ranging from 15 to 150 depending on the amount of collector current. Generally, β is highest for medium collector currents, decreasing for very low and very high collector currents. hfe is small signal AC gain; hFE is large AC signal gain or DC gain. Continue Reading at: Top 10 Transistor ratings

## The device which performs AC to DC conversion is known as

The device which performs AC to DC conversion is known as:

1. Rectifier
2. Inverter
3. Chopper
4. Cycloconverter

Also See MCQs on SCR here

## For a power transistor, if the base current IB is increased keeping VCE constant, then

For a power transistor, if the base current IB is increased keeping VCE constant, then

1. Ic increases
2. Ic decreases
3. Ic remains constant
4. None of these