A power transformer is used to step up an alternating e.m.f. of 220 V to 11 kV to transmit 4.4 kW of power. If the primary coil has 1000 turns, what is the current rating of the secondary ? Assume 100% efficiency for the transformer 

1. 4 A

2. 0.4 A

3. 0.04 A

4. 0.2 A

Subtopic:  Transformer |
 76%
From NCERT
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The primary winding of transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. The secondary will have an output of 

1. 200 V, 50 Hz

2. 2 V, 50 Hz

3. 200 V, 500 Hz

4. 2 V, 5 Hz

Subtopic:  Transformer |
 81%
From NCERT
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A step-down transformer is connected to main supply 200V to operate a 6V, 30W bulb. The current in primary is 

1. 3 A

2. 1.5 A

3. 0.3 A

4. 0.15 A

Subtopic:  Transformer |
 77%
From NCERT
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A transformer has 100 turns in the primary coil and carries 8 A current. If input power is one kilowatt, the number of turns required in the secondary coil to have 500V output will be 

1. 100

2. 200

3. 400

4. 300

Subtopic:  Transformer |
 86%
From NCERT
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A copper rod of length l is rotated about one end perpendicular to the magnetic field B with constant angular velocity ω. The induced e.m.f. between the two ends is 

1. 12Bωl2

2. 34Bωl2

3. Bωl2

4. 2Bωl2

Subtopic:  Motional emf |
 89%
From NCERT
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Two conducting circular loops of radii \(R_1\) and \(R_2\) are placed in the same plane with their centres coinciding. If \(R_1>>R_2\), the mutual inductance \(M\) between them will be directly proportional to:

1. \(\dfrac{R_1}{R_2}\) 2. \(\dfrac{R_2}{R_1}\)
3. \(\dfrac{R^2_1}{R_2}\) 4. \(\dfrac{R^2_2}{R_1}\)
Subtopic:  Mutual Inductance |
 63%
From NCERT
NEET - 2021
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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 \(M\) is at the higher potential
4. \(2RBv\) and \(Q\)  is at the higher potential
Subtopic:  Motional emf |
 66%
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 |
 68%
From NCERT
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A circular loop of radius R carrying current I lies in the x-y plane with its centre at the origin. The total magnetic flux through the x-y plane is 

1. Directly proportional to I

2. Directly proportional to R

3. Directly proportional to R2

4. Zero

Subtopic:  Magnetic Flux |
 53%
From NCERT
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A small square loop of wire of side l is placed inside a large square loop of wire of side L (L > l). The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to 

1. l / L

2. l2 / L

3. L/l

4. L2/l

Subtopic:  Mutual Inductance |
 79%
From NCERT
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