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 |
 84%
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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 weber/m2. 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. \(1.5 \times 10^{-3} V\)





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 |
 75%
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 |
 72%
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, v=vi^. 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 |
 72%
From NCERT
AIPMT - 2009
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