# A conducting circular loop is placed in a uniform magnetic field, $$B=0.025~\text{T}$$ with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of $$1~\text{mm s}^{-1}$$. The induced emf, when the radius is $$2~\text{cm}$$, is: 1. $$2\pi ~\mu\text{V}$$ 2. $$\pi ~\mu\text{V}$$ 3. $$\dfrac{\pi}{2}~\mu\text{V}$$ 4. $$2 ~\mu \text{V}$$

Subtopic: Â Faraday's Law & Lenz Law |
Â 76%
From NCERT
AIPMT - 2010
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The current ($$I$$) in the inductance is varying with time ($$t$$) according to the plot shown in the figure.

Which one of the following is the correct variation of voltage with time in the coil?
 1 2 3 4
Subtopic: Â Self - Inductance |
Â 73%
From NCERT
AIPMT - 2012
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A coil of resistance $$400~\Omega$$ is placed in a magnetic field. The magnetic flux $$\phi~\text{(Wb)}$$ linked with the coil varies with time $$t~\text{(s)}$$ as $$\phi=50t^{2}+4.$$ The current in the coil at $$t=2~\text{s}$$ is:
1. $$0.5~\text{A}$$
2. $$0.1~\text{A}$$
3. $$2~\text{A}$$
4. $$1~\text{A}$$

Subtopic: Â Faraday's Law & Lenz Law |
Â 88%
From NCERT
AIPMT - 2012
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A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced emf is:
 1 twice per revolution. 2 four times per revolution. 3 six times per revolution. 4 once per revolution.

Subtopic: Â Faraday's Law & Lenz Law |
Â 74%
From NCERT
AIPMT - 2013
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The magnetic potential energy stored in a certain inductor is $$25$$ mJ, when the current in the inductor is $$60$$ mA. This inductor is of inductance:
1. $$0.138$$ H
2. $$138.88$$ H
3. $$1.389$$ H
4. $$13.89$$ H

Subtopic: Â Self - Inductance |
Â 69%
From NCERT
NEET - 2018
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In a coil of resistance $$10$$ $$\Omega$$, the induced current developed by changing magnetic flux through it is shown in the figure as a function of time. The magnitude of change in flux through the coil in Weber is:

1. $$2$$
2. $$6$$
3. $$4$$
4. $$8$$

Subtopic: Â Magnetic Flux |
Â 67%
From NCERT
AIPMT - 2012
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The figure shows planar loops of different shapes moving out of or into a region of a magnetic field which is directed normally to the plane of the loop away from the reader. Then:

 1 for the rectangular loop abcd, the induced current is clockwise. 2 for the triangular loop abc, the induced current is clockwise. 3 for the irregularly shaped loop abcd, the induced current is anti-clockwise. 4 none of these.

Subtopic: Â Faraday's Law & Lenz Law |
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A wheel with $$10$$ metallic spokes each $$0.5$$ m long is rotated with a speed of $$120$$ rev/min in a plane normal to the horizontal component of earth’s magnetic field HE at a place. If $$H_E=0.4$$ G at the place, what is the induced emf between the axle and the rim of the wheel? ($$1$$ G=$$10^{-4}$$ T)
1. $$5.12\times10^{-5}$$ T
2. $$0$$
3. $$3.33\times10^{-5}$$
4. $$6.28\times10^{-5}$$

Subtopic: Â Motional emf |
Â 64%
From NCERT
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Two concentric circular coils, one of small radius $${r_1}$$ and the other of large radius $${r_2},$$ such that $${r_1<<r_2},$$  are placed co-axially with centres coinciding. The mutual inductance of the arrangement is:
1. $$\dfrac{\mu_0\pi r_1^2}{3r_2}$$

2. $$\dfrac{2\mu_0\pi r_1^2}{r_2}$$
3. $$\dfrac{\mu_0\pi r_1^2}{r_2}$$
4. $$\dfrac{\mu_0\pi r_1^2}{2r_2}$$

Subtopic: Â Mutual Inductance |
Â 68%
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The expression for the magnetic energy stored in a solenoid in terms of magnetic field $$B$$, area $$A$$ and length $$l$$ of the solenoid is:

 1 $$\dfrac{1}{\mu_0}B^2Al$$ 2 $$\dfrac{1}{2\mu_0}B^2Al$$ 3 $$\dfrac{2}{\mu_0}B^2Al$$ 4 $$\dfrac{3}{2\mu_0}B^2Al$$
Subtopic: Â Self - Inductance |
Â 82%
From NCERT
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