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UNIT I - ELECTROMAGNETISM >> MCQs 101-150
101. In the expression e = Mdi1dt, M represents
a. Mutual induction
b. Mutual inductance
c. Number of lines of force
d. None of these
ans:b
102. If 0.75 V is induced emf and resistance offered by the coil is 200 ohm then induced current is
a. 3.75 A
b. 3. 75 mA
c. 3.75μA
d. 37.5 mA
ans:b
103. If magnetic flux changes from 0.8 Wb to 0.3 Wb, then change in flux is______ Wb.
a. 1.1
b. 0.5
c. -0.5
d. -1.1
ans:c
104. If Number of turns of coil is 200 and if the current is 100mA, then MMF is ________
a. 2000 AT
b. 200 AT
c. 20 AT
d. 0.5 AT
ans:c
105. Leakage factor is also called as
a. Fringing
b. Coefficient of inductance
c. Magnetic coefficient
d. Hopkinson’s coefficient
ans:d
106. Movement of electrons are called as
a. MMF
b. Current
c. Voltage
d. Flux
ans:b
107. Flux density is equal to ________ of flux and area of cross – section.
a. Sum
b. Difference
c. Product
d. Fraction
ans:d
108. NI expression is called
a. MMF
b. EMF
c. Flux linkage
d. Magnetic intensity
ans:a
109. Expression NI/L is called
a. MMF
b. EMF
c. Flux linkage
d. Magnetic field strength
ans:d
110. Expression for mutual inductance is
a. –L dI/dt
b. MdI / dt
c. N2 Ф2/ I1
d. NФ/I
ans:c
111. Faraday’s law of electromagnetic induction is e=
a. –NdФ/dt
b. MdI / dt
c. N2 Ф2 / I1
d. NФ/I
ans:a
112. The constant K in case of mutual induction is equal to
a.Ф1/Ф2
b.Ф2/Ф1
c.Ф1/I1
d.Ф2/I1
ans:d
113. Product of the permeability μoμr is equal to
a. Magnetic flux
b. Magnetic field
c. Magnetic intensity
d. Magnetic flux density / magnetic field
strength
ans:d
114. Expression for self induced emf is
a. –L dI/dt
b. MdI1 / dt
c. N2 Ф2/ I1
d. NФ/I
ans:d
115. __________is normally termed as flux linkages.
a. Ф
b. dФ/dt
c. NФ
d.Ф/I
ans:c
116. The term NФ/I is generally called as______
a. Self inductance
b. Mutual inductance
c. Flux linkage
d. Induced emf
ans:a
117. In the expression for reluctance S = l/μA of a conduced, letter A represents_________ of the conductor.
a. Total area
b. Surface area
c. Cross- sectional area
d. None of these.
ans:c
118. When a current carrying conductor is brought in to magnetic field, the force that moves the conductor depends on
a. direction of current.
b. length of conductor
c. value of current
d.all of the above
ans:d
119. Two current carrying conductors lying parallel to each other are exerting a force of attraction on each other. The currents are
a. Very high
b. in opposite direction
c. low
d. in the same direction
ans:d
120. Two conductors are lying parallel and close to each other. They are carrying currents in opposite directions. The force between them is.
a. Repulsive
b. attractive
c. zero
d. none of these
ans:a
121. When a coil consisting of single turn rotates at uniform speed in magnetic field, the induced emf is____
a. steady
b. alternating
c. changing
d. reversing
ans:b
122. The emf induced in a conductor of length 1 meter moving at a right angles to a uniform magnetic field of flux density 1.5 wb/m2 with velocity of 50 m/s is.
a. 0
b.1.5 v
c. 75 v
d. 100 v
ans:c
123. Which of following statements is incorrect.
a. Whenever flux linking with the coil or circuit changes, an emf is induced.
b. The direction of dynamically induced emf can be determined by Fleming’s right-hand rule.
c. the coefficient of self-inductance is proportional to the square of number of turns on it.
d. Coefficient of coupling for tightly coupled coil is zero.
ans: d
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