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Test: Magnetic Circuits of Electrical Machines - Electrical Engineering (EE) MCQ


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15 Questions MCQ Test GATE Electrical Engineering (EE) Mock Test Series 2025 - Test: Magnetic Circuits of Electrical Machines

Test: Magnetic Circuits of Electrical Machines for Electrical Engineering (EE) 2024 is part of GATE Electrical Engineering (EE) Mock Test Series 2025 preparation. The Test: Magnetic Circuits of Electrical Machines questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Magnetic Circuits of Electrical Machines MCQs are made for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Magnetic Circuits of Electrical Machines below.
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Test: Magnetic Circuits of Electrical Machines - Question 1

The unit of magnetic flux is:

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 1
  • SI Unit of the magnetic flux is Weber.
  • It is a vector quantity.
  • It is measure by the equipment called as Fluxmeter.
  • The magnetic flux per unit area is called as the flux density.
Test: Magnetic Circuits of Electrical Machines - Question 2

Ohm’s law for magnetic circuits is _________.

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 2

Ohm’s law for magnetic circuits states that the MMF is directly proportional to the magnetic flux where reluctance is the constant of proportionality.

Chapter 12– Magnetic Circuits - ppt video online download

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Test: Magnetic Circuits of Electrical Machines - Question 3

What happens to the MMF when the magnetic flux decreases?

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 3

Ohm’s law for the magnetic circuit’s states that the MMF is directly proportional to the magnetic flux hence as the magnetic flux decreases, the MMF also decreases.

Test: Magnetic Circuits of Electrical Machines - Question 4

Calculate the MMF when the magnetic flux is 5Wb and the reluctance is 3A/Wb.

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 4

We know that:
F = ϕS
Substituting the given values from the question, we get MMF = 15At.

Test: Magnetic Circuits of Electrical Machines - Question 5

What is the inductance of a coil in which a current of 0.1A increasing at the rate of 0.5 A/s represents a power flow of 0.5 watt?

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 5

Power flow through the coil is: p = ei

or,

Test: Magnetic Circuits of Electrical Machines - Question 6

A coil of 100 turns is wound on a torroidal magnetic core having a reluctance of 104 AT/Wb. When the coil current is 5 A and is increasing at the rate of 200 A/s, the voltage across the coil would be (assume coil resistance to be 2 Ω)

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 6




Test: Magnetic Circuits of Electrical Machines - Question 7

The field winding of a dc electro-magnet is wound with 960 turns and has a resistance of 50 Ω. The excitation voltage is 230 V and the magnetic flux linking the coil is 5 mWb. The energy stored in the magnetic field is

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 7

Current through the field winding,



So, energy stored in magnetic field

Test: Magnetic Circuits of Electrical Machines - Question 8

The flux in a magnetic core is alternating sinusoidally at a frequency of 600 Hz. The maximum flux density is 2 Tesla and the eddy current loss is 15 Watts. What would be the eddy current loss in the core if the frequency is raised to 800 Hz and the maximum flux density is reduced to 1.5 Tesla?

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 8

We know that eddy current loss,

or

Test: Magnetic Circuits of Electrical Machines - Question 9

Two inductances of 15 mH and 25 mH are connected in series such that their fluxes oppose each other. They are so placed that the coefficient of coupling is 0.8. The value of mutual inductance between them will be 

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 9

Test: Magnetic Circuits of Electrical Machines - Question 10

The property of a material which opposes the production of magnetic flux in it is known as:

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 10
  • Resistance in electrical circuit corresponds to reluctance in magnetic circuit.
  • Reluctance opposes the production of magnetic flux in a magnetic circuit and resistance opposes the flow of current in electrical circuit.
Test: Magnetic Circuits of Electrical Machines - Question 11

Air exhibits

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 11

Magnetic materials are broadly classified into:
1. Paramagnetic
2. Diamagnetic
3. Ferromagnetic based on the intensity of magnetization.

Properties of paramagnetic materials:

  • Paramagnetic substances are those which develop feeble magnetization in the direction of the magnetizing field.
  • When removing the magnetizing field, the paramagnetic material lose their magnetization.
  • Paramagnetic materials have weak magnetization along the direction of the magnetic field.
  • The magnetic lines of force prefer to pass through these materials.
  • The magnetic permeability of paramagnetic materials is slightly greater than one.

Example: Manganese, aluminum, chromium, platinum, air, etc.

Test: Magnetic Circuits of Electrical Machines - Question 12

The laws of electromagnetic induction are summarized in the following equation:

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 12

From Faraday’s law of electromagnetic induction,

(minus sign is due to Lenz’s law).

Test: Magnetic Circuits of Electrical Machines - Question 13

EMF induced in a coil rotating in a uniform magnetic field will be maximum when the

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 13


Hence, emf induced is maximum when di/dt is maximum.

Test: Magnetic Circuits of Electrical Machines - Question 14

The emf induced in a conductor rotating in a bipolar field is

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 14
  • It is nothing but the EMF in a conductor in a rotating magnetic field is sinusoidal and alternating.
  • It may be observed from the process of EMF generation in a conductor.
  • In the initial position, the conductor is parallel with magnetic flux lines. So, there is no EMF.
  • When it reaches perpendicular to flux lines, EMF generation is maximum. After that again it reaches the parallel path to flux lines. So, EMF is zero now.
  • This same action happens again, but it is in the reverse direction. So, again there is an EMF but is in the negative direction.
  • Hence, we get the sinusoidal waveform that has a bipolar field and that is nothing but the AC.
Test: Magnetic Circuits of Electrical Machines - Question 15

The area of his hysteresis loss is a measure of:

Detailed Solution for Test: Magnetic Circuits of Electrical Machines - Question 15

Hysteresis Loss - an overview | ScienceDirect Topics

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