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

Two dissimilar bulbs are connected in series, which bulb will be brighter ?

  1. low resistance bulb

  2. more resistance bulb

  3. high current pass bulb.

  4. low current pass bulb
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Components connected in series are connected along a single path, so the same current flows through all of the components. The current through each of the components is the same, and the voltage across the circuit is the sum of the voltages across each component.
When two bulbs are connected in series the first bulb will receive more current. As the bulb has its own resistance, less current will flow to the next bulb.
Hence the first bulb will glow more.

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

An electric oven of 2 kW power rating is operated in a domestic electric circuit that has a current rating of 5A. If the supply voltage is 220V, what result do you expect?

  1. circuit will be breaked

  2. fuse will blow

  3. both

  4. none
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given,
Power of the oven $(P) = 2kw = 2 \times 103 W$
Voltage supplied $(V) = 220V$
Current $(I) = ? A$
Power $= V \times I$
$\Rightarrow I = P/V = 2 \times 103/220 = 9.09 A$
Since the domestic electric circuit has a current rating of 5A, the flow of 9.09 A by the Oven exceeds the safe limit. Here, fuse will blow and break the circuit.

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

What is the function of distribution box in domestic electrical circuit

  1. It distributes voltage across appliances as per need

  2. It provides isolation between set of appliances and improves reliability

  3. It distributes Losses among all parts of circuit equally

  4. It allows user to manually distribute power as per his need
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Distribution box in domestic electrical circuit provides isolation between appliances and allow them to work paralelly. It also ensures failure in one part do not affect the functioning of the other.

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

A transformer is used to light $100\ W - 110\ V$ lamp from $220\ V$ mains. If the main current is $0.5\ A$, the efficiency of the transformer is

  1. $90$%
  2. $95$%
  3. $96$%
  4. $99$%
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Voltage in primary coil     $V _p = 220$ V

Current in primary coil    $I _p = 0.5$ A
Thus input power     $P _{in} = V _pI _p$
Output power  (in secondary coil )      $P _{out} = 100$ W
$\therefore$  Efficiency of transformer     $\eta = \dfrac{P _{out}}{P _{in}}\times 100$
$\implies   $        $\eta = \dfrac{100}{(220)(0.5)}\times 100 = 90$ %.

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 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

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.