Physics

Electrical Machines and Circuits

754 Questions

Electrical machines and circuits involve the principles of alternating and direct current, transformers, diodes, and power consumption. These concepts are essential for engineering and technical exams. Review these practice questions to test your knowledge of circuit analysis.

Transformers and impedanceAlternating and direct currentCircuit components and diodesPower consumption calculations

Electrical Machines and Circuits Questions

Multiple choice

The effect of current shunt feedback in an amplifier is to

  1. increase the input resistance and decrease the output resistance

  2. increase both input and output resistances

  3. decrease both input and output resistances

  4. decrease the input resistance and increase the output resistance
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The given solution is right.                    Here  Ri  = input resistance without feedback                              Rif  = input resistance with feedback                              R of  = output resistance with feedback                  

Multiple choice

The Zener diode in the regulator circuit shown in figure has a Zener voltage of 5.8 Volts and a Zener knee current of 0.5 mA. The maximum load current drawn from this circuit ensuring proper functioning over the input voltage range between 20 and 30 Volts, is

  1. 23.7 mA

  2. 14.2 mA

  3. 13.7 mA

  4. 24.2 mA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\text{The maximum load current will be at maximum input voltage i.e} \\ V_{max} = 30 V i.e \\ or \hspace{1cm} \frac{30 - 5.8}{1K} = I_L = 0.5 m \\ or \hspace{1cm} I_L = 24.2 - 0.5 = 23.7 mA$

Multiple choice

Voltage series feedback (also called series-shunt feedback) results in

  1. increase in both input and output impedances

  2. decrease in both input and output impedances

  3. increase in input impedance and decrease in output impedance

  4. decrease in input impedance and increase in output impedance
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In voltage series feedback amplifier, input impedance increases by factor $(1+A\beta)$ and output impedance decreases by the factor $(1+A\beta)$

$$R_{if} = R_i(1+A\beta)\\

R_{of} = \dfrac{R_0}{(1+A\beta)} $$

Multiple choice

An ideal op-amp is an ideal

  1. voltage controlled current source

  2. voltage controlled voltage source

  3. current controlled current source

  4. current controlled voltage source
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An ideal OPAMP is an ideal voltage controlled voltage source.

Multiple choice

The thin wire in a bulb is called

  1. fuse

  2. circuit

  3. filament

  4. wire

  5. element
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is the correct answer as the thin connecting wire inside a bulb is called its filament.