Physics

Electrical Machines and Circuits

720 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

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.

Multiple choice

Which of the following statements is/are incorrect?

a. Current does not flow if a circuit is complete. b. An electric circuit is opened when the switch is in the ‘ON’ position. c. A bulb will glow only when the electric circuit is open.

  1. a only

  2. b only

  3. c only

  4. b and c

  5. a, b and c
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct answer as all statements are incorrect. Current flows only if a circuit is complete. An electric circuit is closed when the switch is in the ‘ON’ position. A bulb will glow only when the electric circuit is closed.

Multiple choice

Which of the following cause(s) excessive currents in electrical circuit?

  1. Overload in circuit

  2. Direct touching of wires

  3. Insulation on the wires coming off due to wear and tear

  4. Connection of many devices to a single socket

  5. All of the above
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct option as all of the above are the reasons for excessive currents in electrical circuit.

Multiple choice

Which of the following statements is/are correct?

a. Different types of fuse are used in different types of circuits. b. These days, MCBs are used in place of fuses. c. Any wire or strip of metal can be used in place of a fuse.

  1. only a and b

  2. only b and c

  3. only a and c

  4. a, b and c

  5. only a
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct answer as both statements are correct. Different types of fuse are used in different types of circuits. These days, MCBs are used in place of fuses.