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 chemical effects of electric current study about cells electric cell types of cells

How many different colors of wire are needed to ignite the bulb when connected with cell ?

  1. 2

  2. 1

  3. 4

  4. 6
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are two wires needed to connect and ignite the bulb when connected with cell.

$(i)$ To connect the terminal of the cell to the terminal of the bulb.
$(ii)$ The tungsten wire which will get lighten up.
Option $A$ is the correct answer. 

Multiple choice physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

Which of the following is true for a toroid?

  1. low inductance and Q factor

  2. high inductance and Q factor

  3. high inductance and low Q-factor

  4. low inductance and high Q-factor
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Due to the symmetry and being closed loop core.
Toroid has higher magnetic field and thus higher inductor and Q-factor

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

A bulb  is connected  to an ideal battery of emf 10 V so that the resulting current is 10 mA . When the bulb is connected to 220 V mains (ideal), the current is 50 mA. choose the correct alternative

  1. the resistance of the bulb is 1 k ohm and in the second case, it is 4.4 k ohm

  2. it is not possible since ohm's law is not followed

  3. the increase in resistance is due to heating of the filament of the bulb when it is connected to 220 V main

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A bulb is connected to an ideal battery of emf$=10V$

Current$=10mA\=10\times10^{-3}A$
when the bulb connected $220V$ (main)
and current$=50\times10^{-3}A$
Using Ohm's law,
First case:
$I=\cfrac{10\times10^3}{10}=1K\Omega$
Second case 
$I^{\prime}=\cfrac{220\times10^3}{50}=4.4k\Omega$
Hence answer $(A)$ will be correct.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

In a transformer the immediate cause of the induced A. C. in the secondary coil is

  1. A varying electric field

  2. A varying magnetic field

  3. A motion of the secondary coil

  4. Efficiency of the operator
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Faraday's law of induction, a changing magnetic flux through a coil induces an electromotive force (EMF). In a transformer, the alternating current in the primary coil creates a varying magnetic field that links with the secondary coil.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

Alternating current is one which changes in its :

  1. direction

  2. magnitude

  3. magnitude and direction both

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

Answer is C.

An alternating current (AC) is an electric current of which magnitude and direction vary, unlike direct current, whose direction remains constant.
The usual waveform of an AC power circuit is a sine wave, because this leads to the most efficient transmission of energy. However, in certain applications different waveforms are used, such as triangular or square waves.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

The simplest type of AC voltage or current is the one which

  1. Varies exponentially

  2. Varies sinusoidally

  3. Varies linearly

  4. Does not vary uniformly
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:-

AC wave can be of any form but mathematical techniques are easier for the sine waveform such as any wave can be represent as combination of sine waves using fourier transform and integration and differentiation of sine wave is sine wave only.

Option B is correct.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

Choose the incorrect statement.

  1. Alternating current is oscillatory

  2. Electric power is transmitted over long distances using alternating current.

  3. Frequency of alternating current in India is 50 Hz.

  4. Alternating current can be used for electrolysis of copper chloride.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Even if it were current-limited, alternating current (AC) would not be appropriate for electrolysis. Because the "cathode" and "anode" will be constantly switching places as the polarities will change with time. Therefore, direct current (DC) is used for electrolysis.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

Why the current produced by the generator is  called as alternating current.

  1. continuous decrease and increase of current occurs.

  2. after every half cycle direction of flow of current is reversed.

  3. both

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

We may say that after every half cycle direction of flow of current is reversed. Because of this reason the current produced by the generator is also called as alternating current.

Multiple choice eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are 

  1. friction and windage losses

  2. copper losses

  3. hysteresis and eddy current losses

  4. none of the above

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are hysteresis and eddy current losses The losses that can occur in a material are: Iron losses: Iron loss is caused by the alternating flux in the core and consists of hysteresis and eddy current losses. of coercivity on the curve. (The reversed magnetizing force has flipped enough of the domains so that the net flux within the material is zero.)

Multiple choice physics household circuits electric switch switch electrical circuit

A switch is always connected to the :

  1. Live wire

  2. Neutral wire

  3. Earth wire

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A switch is always connected to live wire. The purpose of the switch is to break or connect an electric circuit, but they must be correctly connected at home.

Multiple choice physics household circuits electric switch switch electrical circuit

Why are switches not connected to neutral wire?

  1. Because there will be overheating

  2. No current will flow through the appliance

  3. Fuse will blow

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

If the switches are connected to neutral wire, no current will flow through the appliance and hence it will not operate.