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 physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Why is parallel arrangement used in domestic wiring?

  1. For getting same potential difference across each electrical appliance.

  2. For getting different potential difference across each electrical appliance.

  3. For getting high potential difference across each electrical appliance.

  4. For getting low potential difference across each electrical appliance.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The usage of parallel arrangement in domestic circuits has many advantages.

  • Each circuit will have the same potential difference which is equal to  the potential difference of the supply line. As a result, each electrical appliance will work under constant voltage.
  • When two or more appliances are used at the same time, each appliance will be able to draw the current as needed. The appliances having low resistance will draw higher current and vice versa.
  • When distribution circuits are in parallel, then each circuit operates separately. So, if one of the distribution circuits gets overloaded, only the fuse in that circuit will be blown off. The other distribution circuits will remain unaffected.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

The armature current in D.C motor is maximum when the motor has -


  1. picked up maximum speed

  2. just started

  3. intermediate speed

  4. just been switched off
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a DC motor, the back emf is proportional to the speed of the motor (E_b = k * omega). The armature current is given by I_a = (V - E_b) / R_a. When the motor has just started, its speed is zero, so the back emf is zero, resulting in the maximum possible armature current.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

The line that draws power supply to your house from Street has

  1. $220\sqrt{2}$ average voltage.

  2. 220 V average voltage
  3. voltage and current Out of phase by $\pi/2$
  4. voltage and current possibly differing in phase $\phi$ such that $| \phi| < \dfrac{\pi}{2}.$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As the line has some resistance $(R \, \neq \, 0)$. Also, line that draws power supply has some inductance and capacitance, hence voltage and current differ in phase $\phi$ such that $|\phi| \, < \, \dfrac{\pi}{2}$.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Which arrangement is used for domestic circuits ?

  1. Series

  2. Parallel

  3. Series and parallel both

  4. None
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For Domestic circuits parallel arrangement is always used because:

  1. In parallel circuits, if one electrical appliance stop working due to some effect then all other appliances keep working normally.
  2. In parallel circuit, each electrical appliance has own switch due to which it can be turn off or on independently, without effecting  other appliances.
  3. In parallel circuits, each electrical appliance gets same voltage as that of the power supply line.
  4. In the parallel connection of electrical appliances, the overall resistance of the house hold circuit is reduced due to which the current from the power supply is high.

Multiple choice

Why are analog signals prone to distortion & decreased transmission quality?

  1. noise can interrupt the signals

  2. the frequency of waves changes quickly

  3. the amplitude of a wave is too high

  4. each phase cannot store enough information
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Analog signals are continuous waves that are highly susceptible to interference from environmental noise, which alters the signal and degrades quality.

Multiple choice

What happens to a circuit if a fuse gets blown?

  1. the circuit opens

  2. the circuit gets replicated to make an alternative

  3. the circuit closes

  4. it shuts off the fuse below it
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A fuse is designed to break the circuit when too much current flows through it. When the fuse blows, it creates a break in the path, which is an open circuit.

Multiple choice

Light bulbs connected in a parallel circuit would do which of the following?

  1. all lights would stay on even if one went out

  2. all lights would go out if one went out

  3. all lights would get brighter if one went out

  4. all lights would blink if one went out
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a parallel circuit, each component has its own independent path to the power source. Therefore, if one bulb burns out, the others remain connected and continue to light up.