Electromagnetic Theory Questions and Answers – Maxwell Law in Time Static Fields

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This set of Electromagnetic Theory Multiple Choice Questions & Answers (MCQs) focuses on “Maxwell Law in Time Static Fields”.

1. Calculate the emf in a material with flux linkage of 3.5t2 at 2 seconds.
a) 3.5
b) -7
c) -14
d) 28
View Answer

Answer: c
Explanation: The emf induced in a material with flux linkage is given by Vemf = -dλ/dt. On substituting λ= 3.5t2, we get emf = -7t. At time t = 2sec, the emf will be -14 units.
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2. Find the emf induced in a coil of 60 turns with a flux rate of 3 units.
a) -60
b) -180
c) 60
d) 180
View Answer

Answer: b
Explanation: The emf induced is the product of the turns and the flux rate. Thus Vemf = -Ndφ/dt. On substituting N = 60 and dφ/dt = 3, we get emf as -60 x 3 = -180 units.

3. Find the electric field intensity of a charge 2.5C with a force of 3N.
a) -7.5
b) 7.5
c) 2.5/3
d) 3/2.5
View Answer

Answer: d
Explanation: The electric field intensity is the electric force per unit charge. It is given by E = F/q. On substituting F = 2.5 and q = 3, we get E = 3/2.5 units.
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4. The electric field intensity of a field with velocity 10m/s and flux density of 2.8 units is
a) 0.28
b) 28
c) 280
d) 10/2.8
View Answer

Answer: b
Explanation: The electric field is the product of the velocity and the magnetic flux density given by E = v x B. On substituting v = 10 and B = 2.8, we get E = 10 x 2.8 = 28 units.

5. The line integral of the electric field intensity is
a) Mmf
b) Emf
c) Electric potential
d) Magnetic potential
View Answer

Answer: b
Explanation: From the Maxwell first law, the transformer emf is given by the line integral of the electric field intensity. Thus the emf is given by ∫ E.dl.
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6. Which of the following relations is correct?
a) MMF = ∫ B.dl
b) MMF = ∫ H.dl
c) EMF = ∫ E.dl
d) EMF = ∫ D.dl
View Answer

Answer: c
Explanation: The emf induced in a material is given by the line integral of the electric field intensity. Thus EMF = ∫ E.dl is the correct relation.

7. For static fields, the curl of E will be
a) Rotational
b) Irrotational
c) Solenoidal
d) Divergent
View Answer

Answer: b
Explanation: For static fields, the charges will be constant and the field is constant. Thus curl of the electric field intensity will be zero. This implies the field is irrotational.
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8. The line integral of which parameter is zero for static fields?
a) E
b) H
c) D
d) B
View Answer

Answer: a
Explanation: The field is irrotational for static fields. Thus curl of E is zero. From Stokes theorem, the line integral of E is same as the surface integral of the curl of E. Since it is zero, the line integral of E will also be zero.

9. The magnitude of the conduction current density for a magnetic field intensity of a vector yi + zj + xk will be
a) 1.414
b) 1.732
c) -1.414
d) -1.732
View Answer

Answer: b
Explanation: From the Ampere circuital law, the curl of H is the conduction current density. The curl of H = yi + zj + xk is –i – j – k. Thus conduction current density is –i – j – k. The magnitude will be √(1 + 1 + 1) = √3 = 1.732 units.
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10. The charge density of a field with a position vector as electric flux density is given by
a) 0
b) 1
c) 2
d) 3
View Answer

Answer: d
Explanation: The Gauss law for electric field states that the divergence of the electric flux density is the charge density. Thus Div(D) = ρ. For D as a position vector, the divergence of the position vector D will be always 3. Thus the charge density is also 3.

Sanfoundry Global Education & Learning Series – Electromagnetic Theory.
To practice all areas of Electromagnetic Theory, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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