# 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:  Faraday's Law & Lenz Law |
74%
From NCERT
AIPMT - 2013
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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:  Faraday's Law & Lenz Law |
87%
From NCERT
AIPMT - 2012
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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:  Self - Inductance |
73%
From NCERT
AIPMT - 2012
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The current $$i$$ in a coil varies with time as shown in the figure. The variation of induced emf with time would be:

 1 2 3 4
Subtopic:  Faraday's Law & Lenz Law |
69%
From NCERT
AIPMT - 2011
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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. $$\frac{\pi}{2}~\mu\text{V}$$
4. $$2 ~\mu \text{V}$$

Subtopic:  Faraday's Law & Lenz Law |
75%
From NCERT
AIPMT - 2010
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A conducting circular loop is placed in a uniform magnetic field of 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at a rate of 2 mm/s. The induced e.m.f. in the loop when the radius is 2 cm is:

1. $$3.2\pi ~\mu V$$

2. $$4.8\pi ~\mu V$$

3. $$0.8\pi ~\mu V$$

4. $$1.6\pi ~\mu V$$

Subtopic:  Faraday's Law & Lenz Law |
69%
From NCERT
AIPMT - 2009
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A rectangular, a square, a circular, and an elliptical loop, all in the (x-y) plane, are moving out of a uniform magnetic field with a constant velocity, $\stackrel{\to }{\mathrm{v}}=\mathrm{v}\stackrel{^}{\mathrm{i}}$. The magnetic field is directed along the negative z-axis direction. The induced emf, during the passage of these loops out of the field region, will not remain constant for:

 1 the rectangular, circular, and elliptical loops. 2 the circular and the elliptical loops. 3 only the elliptical loop. 4 any of the four loops.

Subtopic:  Motional emf |
71%
From NCERT
AIPMT - 2009
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A long solenoid has $$500$$ turns. When a current of $$2$$ A is passed through it, the resulting magnetic flux linked with each turn of the solenoid is $$4\times 10^{-3}$$ Wb. The self-inductance of the solenoid is:
1. $$2.5$$ H
2. $$2.0$$ H
3. $$1.0$$ H
4. $$4.0$$ H

Subtopic:  Self - Inductance |
78%
From NCERT
AIPMT - 2008
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A circular disc of radius $$0.2~\text{m}$$ is placed in a uniform magnetic field of induction $$\frac{1}{\pi}~\text{Wb/m}^{2}$$ in such a way that its axis makes an angle of $$60^{\circ}$$ with $$\vec{B}.$$ The magnetic flux linked with the disc is:
1. $$0.02~\text{Wb}$$
2. $$0.06~\text{Wb}$$
3. $$0.08~\text{Wb}$$
4. $$0.01~\text{Wb}$$
Subtopic:  Magnetic Flux |
84%
From NCERT
AIPMT - 2008
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The primary and secondary coils of a transformer have $$50$$ and $$1500$$ turns respectively. If the magnetic flux $$\phi$$ linked with the primary coil is given by $$\phi=\phi_0+4t,$$ where $$\phi$$ is in Weber, $$t$$ is time in seconds, and $$\phi_0$$  is a constant, the output voltage across the secondary coil is:
1. $$90~\mathrm{V}$$
2. $$120~\mathrm{V}$$
3. $$220~\mathrm{V}$$
4. $$30~\mathrm{V}$$

Subtopic:  Magnetic Flux |
80%
From NCERT
AIPMT - 2007
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