Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R):

 Assertion (A): When a piece of non-metal and a metal are dropped from the same height near the surface of the earth, the non-metallic piece will reach the ground first. Reason (R): Induced current in metal will decrease the acceleration.

In the light of the above statements choose the correct answer from the options given below:

 1 Both (A) and (R) are true and (R) is the correct explanation of (A). 2 Both (A) and (R) are true but (R) is not the correct explanation of (A). 3 (A) is true but (R) is false. 4 Both (A) and (R) are false.

Subtopic:  Motional emf |
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An aeroplane in which the distance between the tips of wings is 50 m is flying horizontally with a speed of 360 km/hr over a place where the vertical component of earth magnetic field is $2.0×{10}^{-4}$ $\mathrm{weber}/{\mathrm{m}}^{2}$. The potential difference between the tips of wings would be:

 1 0.1 V 2 1.0 V 3 0.2 V 4 0.01 V
Subtopic:  Motional emf |
81%
From NCERT
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A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 ms-1 at right angle to the horizontal component of the earth's magnetic field, $$0.30 \times 10^{-4} \mathrm{~Wb} \mathrm{~m}^{-2}$$
. The instantaneous value of the emf induced in the wire is:

 1 $$2.5 \times 10^{-3} V$$ 2 $$1.5 \times 10^{-4} V$$ 3 $$2.5 \times 10^{-4} V$$ 4 $$1.5 \times 10^{-3} V$$

$\begin{array}{r}\end{array}$

Subtopic:  Motional emf |
81%
From NCERT
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A magnetic rod is inside a coil of wire which is connected to an ammeter. If the rod is stationary, which of the following statements is true?

 1 The rod induces a small current. 2 The rod loses its magnetic field. 3 There is no induced current. 4 None of these.

Subtopic:  Motional emf |
80%
From NCERT
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A square metallic wire loop of side 0.1 m and resistance of $$1~\Omega$$ is moved with a constant velocity in a magnetic field of $$2~\mathrm{wb/m^2}$$ as shown in the figure. The magnetic field is perpendicular to the plane of the loop and the loop is connected to a network of resistances. What should be the velocity of the loop so as to have a steady current of 1 mA in the loop?

 1 1 cm/sec 2 2 cm/sec 3 3 cm/sec 4 4 cm/sec
Subtopic:  Motional emf |
76%
From NCERT
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A $$1~\text{m}$$ long metallic rod is rotating with an angular frequency of $$400~\text{rad/s}$$ about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of $$0.5~\text{T}$$ parallel to the axis exists everywhere. The emf induced between the center and the ring is:
1. $$200~\text{V}$$
2. $$100~\text{V}$$
3. $$50~\text{V}$$
4. $$150~\text{V}$$

Subtopic:  Motional emf |
75%
From NCERT
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A wire cd of length l and mass m is sliding without friction on conducting rails ax and by as shown. The vertical rails are connected to each other with a resistance R between a and b. A uniform magnetic field B is applied perpendicular to the plane abcd such that cd moves with a constant velocity of:

 1 $${mgR \over Bl}$$ 2 $${mgR \over B^2l^2}$$ 3 $${mgR \over B^3l^3}$$ 4 $${mgR \over B^2l}$$
Subtopic:  Motional emf |
75%
From NCERT
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A conductor ABOCD moves along its bisector with a velocity of 1 m/s through a perpendicular magnetic field of $$1~\mathrm{wb/m^2}$$, as shown in fig. If all the four sides are of 1 m length each, then the induced emf between points A and D is:

1. 0

2. 1.41 volt

3. 0.71 volt

4. None of the above

Subtopic:  Motional emf |
73%
From NCERT
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Consider the situation shown in the figure. The wire AB is sliding on the fixed rails with a constant velocity. If the wire AB is replaced by semicircular wire, the magnitude of the induced current will:

 1 increase. 2 remain the same. 3 decrease. 4 increase or decrease depending on whether the semicircle bulges towards the resistance or away from it.
Subtopic:  Motional emf |
70%
From NCERT
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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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