Test: Magnetic Circuits

# Test: Magnetic Circuits

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## 10 Questions MCQ Test Electromagnetic Fields Theory (EMFT) | Test: Magnetic Circuits

Test: Magnetic Circuits for Electrical Engineering (EE) 2023 is part of Electromagnetic Fields Theory (EMFT) preparation. The Test: Magnetic Circuits questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Magnetic Circuits MCQs are made for Electrical Engineering (EE) 2023 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Magnetic Circuits below.
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Test: Magnetic Circuits - Question 1

### The induced emf in a material opposes the flux producing it. This is

Detailed Solution for Test: Magnetic Circuits - Question 1

The induced emf in a material under the influence of a magnetic field will oppose the flux that produces it. This is indicated by a negative sign in the emf equation. This phenomenon is called Lenz law.

Test: Magnetic Circuits - Question 2

### The flux lines of two energised coils overlapping on each other will give

Detailed Solution for Test: Magnetic Circuits - Question 2

Flux lines are the magnetic lines of force of a magnetic material. Since the flux is overlapping, the total flux of the two coils together will be high. Thus it is an aiding flux. Also this type of overlapping is possible only when the two coils are back to back or in series connection.

Test: Magnetic Circuits - Question 3

### Calculate the reluctance of the material with a mmf of 3.5 units and flux of 7units.

Detailed Solution for Test: Magnetic Circuits - Question 3

The reluctance is defined as the ratio of the mmf and the flux. It is given by S = mmf/φ. On substituting mmf = 3.5 and φ = 7, we get S = 3.5/7 = 0.5 units.

Test: Magnetic Circuits - Question 4

Calculate the reluctance of a material with length 2π x 10-4 in air with area 0.5.

Detailed Solution for Test: Magnetic Circuits - Question 4

The reluctance is given by S = L/μ A, where L is the length, A is the area and μ is the permeability. On substituting L = 2π x 10-4, A = 0.5 and μ = 4π x 10-7, we get S = 103/(2 x0.5) = 1000 units.

Test: Magnetic Circuits - Question 5

The line integral of the magnetic field intensity is given by

Detailed Solution for Test: Magnetic Circuits - Question 5

The line integral of H is given by ∫H. dl. From Ampere law it can be related to the current density and hence the current element NI for a coil of N turns. Thus, ∫H. dl = NI.

Test: Magnetic Circuits - Question 6

The magnetic energy of a magnetic material is given by

Detailed Solution for Test: Magnetic Circuits - Question 6

The magnetic energy of a material is given by half of the product of the magnetic flux density and the magnetic field intensity. It is represented as BH/2. Since B = μH, we can also write as μH2 or B2/2μ.

Test: Magnetic Circuits - Question 7

The energy in a magnetic material is due to which process?

Detailed Solution for Test: Magnetic Circuits - Question 7

The energy in a magnetic material is due to the formation of magnetic dipoles which are held together due to magnetic force. This gives energy to the material. Hence it is due to magnetization process.

Test: Magnetic Circuits - Question 8

The resistance in a magnetic material is called as

Detailed Solution for Test: Magnetic Circuits - Question 8

The reluctance of a magnetic material is the ability of the material to oppose the magnetic flux. It is the ratio of the magnetic motive force mmf to the flux.

Test: Magnetic Circuits - Question 9

Which of the following relations is correct?

Detailed Solution for Test: Magnetic Circuits - Question 9

The reluctance is also defined by the ratio of the current element to the flux. In other words, mmf = NI. Thus S = NI/φ. We get the relation NI = Sφ.

Test: Magnetic Circuits - Question 10

Ampere turn is equivalent to which element?

Detailed Solution for Test: Magnetic Circuits - Question 10

Ampere turn refers to the current element, which is the product of the turns and the current. It is given by NI. From the definition of reluctance, S = NI/φ. Thus NI = Sφ is the best equivalent.

## Electromagnetic Fields Theory (EMFT)

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## Electromagnetic Fields Theory (EMFT)

11 videos|46 docs|62 tests