# A uniform magnetic field is restricted within a region of radius $$r$$. The magnetic field changes with time at a  rate $$\frac{dB}{dt}$$. Loop $$1$$ of radius $$R>r$$ is enclosed within the region $$r$$ and loop $$2$$ of radius $$R$$ is outside the region of the magnetic field as shown in the figure. Then, the emf generated is:             1.  zero in loop $$1$$ and zero in loop $$2$$ 2.  $$-\frac{dB}{dt}\pi r^2$$ in loop $$1$$ and zero in loop $$2$$ 3.   $$-\frac{dB}{dt}\pi R^2$$ in loop $$1$$ and zero in loop $$2$$ 4.   zero in loop $$1$$ and not defined in loop $$2$$

Subtopic: Â Faraday's Law & Lenz Law |
Â 69%
From NCERT
NEET - 2016
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A long solenoid has $$1000$$ turns. When a current of $$4~\text{A}$$ flows through it, the magnetic flux linked with each turn of the solenoid is $$4\times 10^{-3}~\text{Wb}$$. The self-inductance of the solenoid is:
1. $$3~\text{H}$$
2. $$2~\text{H}$$
3. $$1~\text{H}$$
4. $$4~\text{H}$$
Subtopic: Â Self - Inductance |
Â 88%
From NCERT
NEET - 2016
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An electron moves on a straight-line path $$XY$$ as shown. The $$\mathrm{abcd}$$ is a coil adjacent to the path of electrons. What will be the direction of current if any, induced in the coil?

 1 $$\mathrm{abcd}$$ 2 $$\mathrm{adcb}$$ 3 The current will reverse its direction as the electron goes past the coil 4 No current included

Subtopic: Â Faraday's Law & Lenz Law |
Â 74%
From NCERT
NEET - 2015
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A conducting square frame of side $$a$$ and a long straight wire carrying current $$I$$ are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity $$v.$$ The emf induced in the frame will be proportional to:

1. $$\frac{1}{x^2}$$
2. $$\frac{1}{(2 x-a)^2}$$
3. $$\frac{1}{(2 x+a)^2}$$
4. $$\frac{1}{(2 x-a)(2 x+a)}$$

Subtopic: Â Motional emf |
Â 72%
From NCERT
NEET - 2015
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A thin semicircular conducting the ring $$(PQR)$$ of radius $$r$$ is falling with its plane vertical in a horizontal magnetic field $$B,$$ as shown in the figure. The potential difference developed across the ring when it moves with speed $$v$$ is:

 1 zero 2 $$Bv\pi r^{2}/2$$ and $$P$$ is at a higher potential 3 $$\pi rvB$$ and $$R$$ is at a higher potential 4 $$2BvR$$ and $$R$$ is at higher potential
Subtopic: Â Motional emf |
Â 74%
From NCERT
AIPMT - 2014
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A coil of self-inductance $$L$$ is connected in series with a bulb $$B$$ and an AC source. The brightness of the bulb decreases when:
 1 number of turns in the coil is reduced. 2 a capacitance of reactance $$X_C = X_L$$ is included in the same circuit. 3 an iron rod is inserted in the coil. 4 frequency of the AC source is decreased.
Subtopic: Â Self - Inductance |
Â 67%
From NCERT
AIPMT - 2013
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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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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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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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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: Â Faraday's Law & Lenz Law |
Â 69%
From NCERT
AIPMT - 2011
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