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%
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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%
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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%
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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%
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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%
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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%
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When a conducting wire XY is moved towards the right, a current flows in the anti-clockwise direction. Direction of magnetic field at point O is:

1.  parallel to the motion of wire.
2.  along with XY.
3.  perpendicular outside the paper.
4.  perpendicular inside the paper.
Subtopic:  Motional emf |
 72%
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An electric potential difference will be induced between the ends of the conductor shown in the diagram when the conductor moves in the direction of:

    

1. P
2. Q
3. L
4. M

Subtopic:  Motional emf |
 70%
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A rod having length l and resistance R0 is moving with speed v as shown in the figure. The current through the rod is:
               
1. BlvR1R2R1+R2+R0

2. Blv1R1+1R2+1Ro2

3. BlvR1+R2+R0

4. Blv1R1+1R2+1R0

Subtopic:  Motional emf |
 65%
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A thin semicircular conducting ring of radius R is falling with its plane vertical in a horizontal magnetic induction B. At the position MNQ, the speed of the ring is v and the potential difference developed across the ring is:

   

1.  Zero
2. \(B v \pi R^2 / 2\) and M is at the higher potential 
3. \(2 R B v\) and is at the higher potential
4. \(2RBv\) and Q  is at the higher potential

Subtopic:  Motional emf |
 65%
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