Electromagnetic Induction Practice Questions - DPP for JEE

 Page 1


PART-I (Single Correct MCQs)
1. A metal rod of length l cuts across a uniform magnetic field B with a 
velocity v. If the resistance of the circuit of which the rod forms a part
is r, then the force required to move the rod is
(a)
(b)
(c)
(d)
2. Three solenoid coils of same dimension, same number of turns and
same number of layers of windings are taken. Coil 1 with inductance L
1
was wound using a Mn wire of resistance 11 ?/m, coil 2 with
Page 2


PART-I (Single Correct MCQs)
1. A metal rod of length l cuts across a uniform magnetic field B with a 
velocity v. If the resistance of the circuit of which the rod forms a part
is r, then the force required to move the rod is
(a)
(b)
(c)
(d)
2. Three solenoid coils of same dimension, same number of turns and
same number of layers of windings are taken. Coil 1 with inductance L
1
was wound using a Mn wire of resistance 11 ?/m, coil 2 with
inductance L
2
 was wound using the similar wire but the direction of
winding was reversed in each layer; coil 3 with inductance L
3
 was
wound using a superconducting wire. The self inductance of the coils
L
1
, L
2
,  L
3 
are
(a) L
1 
= L
2
= L
3
(b) L
1 
= L
2
;  L
3 
= 0
(c) L
1
= L
3
; L
2
= 0
(d) L
1 
> L
2 
> L
3
3. 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, . 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
(a) the circular and the elliptical loops.
(b) only the elliptical loop.
(c) any of the four loops.
(d) the rectangular, circular and elliptical loops.
4. A metal ring is held horizontally and bar magnet is dropped through the
ring with its length along the axis of the ring. The acceleration of the
falling magnet
(a) is equal to g
(b) is less than g
(c) is more than g
(d) depends on the diameter of ring and length of magnet
5. Which of the following figure correctly depicts the Lenz’s law. The
arrows show the movement of the labelled pole of a bar magnet into a
closed circular loop and the arrows on the circle show the direction of
the induced current
Page 3


PART-I (Single Correct MCQs)
1. A metal rod of length l cuts across a uniform magnetic field B with a 
velocity v. If the resistance of the circuit of which the rod forms a part
is r, then the force required to move the rod is
(a)
(b)
(c)
(d)
2. Three solenoid coils of same dimension, same number of turns and
same number of layers of windings are taken. Coil 1 with inductance L
1
was wound using a Mn wire of resistance 11 ?/m, coil 2 with
inductance L
2
 was wound using the similar wire but the direction of
winding was reversed in each layer; coil 3 with inductance L
3
 was
wound using a superconducting wire. The self inductance of the coils
L
1
, L
2
,  L
3 
are
(a) L
1 
= L
2
= L
3
(b) L
1 
= L
2
;  L
3 
= 0
(c) L
1
= L
3
; L
2
= 0
(d) L
1 
> L
2 
> L
3
3. 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, . 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
(a) the circular and the elliptical loops.
(b) only the elliptical loop.
(c) any of the four loops.
(d) the rectangular, circular and elliptical loops.
4. A metal ring is held horizontally and bar magnet is dropped through the
ring with its length along the axis of the ring. The acceleration of the
falling magnet
(a) is equal to g
(b) is less than g
(c) is more than g
(d) depends on the diameter of ring and length of magnet
5. Which of the following figure correctly depicts the Lenz’s law. The
arrows show the movement of the labelled pole of a bar magnet into a
closed circular loop and the arrows on the circle show the direction of
the induced current
(a)
(b)
(c)
(d)
6. A metallic rod of length ‘ l’ is tied to a string of
length 2 l and made to rotate with angular speed
? on a horizontal table with one end of the string
fixed. If there is a vertical magnetic field ‘B’ in
the region, the e.m.f. induced across the ends of
the rod is
(a)
(b)
(c)
(d)
7. Figure shows a conducting rod of negligible resistance that can slide on
smooth U-shaped rail made of wire of resistance 1?/m. Position of the
Page 4


PART-I (Single Correct MCQs)
1. A metal rod of length l cuts across a uniform magnetic field B with a 
velocity v. If the resistance of the circuit of which the rod forms a part
is r, then the force required to move the rod is
(a)
(b)
(c)
(d)
2. Three solenoid coils of same dimension, same number of turns and
same number of layers of windings are taken. Coil 1 with inductance L
1
was wound using a Mn wire of resistance 11 ?/m, coil 2 with
inductance L
2
 was wound using the similar wire but the direction of
winding was reversed in each layer; coil 3 with inductance L
3
 was
wound using a superconducting wire. The self inductance of the coils
L
1
, L
2
,  L
3 
are
(a) L
1 
= L
2
= L
3
(b) L
1 
= L
2
;  L
3 
= 0
(c) L
1
= L
3
; L
2
= 0
(d) L
1 
> L
2 
> L
3
3. 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, . 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
(a) the circular and the elliptical loops.
(b) only the elliptical loop.
(c) any of the four loops.
(d) the rectangular, circular and elliptical loops.
4. A metal ring is held horizontally and bar magnet is dropped through the
ring with its length along the axis of the ring. The acceleration of the
falling magnet
(a) is equal to g
(b) is less than g
(c) is more than g
(d) depends on the diameter of ring and length of magnet
5. Which of the following figure correctly depicts the Lenz’s law. The
arrows show the movement of the labelled pole of a bar magnet into a
closed circular loop and the arrows on the circle show the direction of
the induced current
(a)
(b)
(c)
(d)
6. A metallic rod of length ‘ l’ is tied to a string of
length 2 l and made to rotate with angular speed
? on a horizontal table with one end of the string
fixed. If there is a vertical magnetic field ‘B’ in
the region, the e.m.f. induced across the ends of
the rod is
(a)
(b)
(c)
(d)
7. Figure shows a conducting rod of negligible resistance that can slide on
smooth U-shaped rail made of wire of resistance 1?/m. Position of the
conducting rod at t = 0 is shown. A time t dependent magnetic field B =
2t tesla is switched on at t = 0.
At t = 0, when the magnetic field is switched  on, the conducting rod is
moved to the left at constant speed 5cm/s by some external means. The
rod moves perpendicular to the rails. At t = 2s, induced emf has
magnitude
(a) 0.12V
(b) 0.08V
(c) 0.04V
(d) 0.02 V
8. A square loop of side a is rotating about its
diagonal with angular velocity ? in a
perpendicular magnetic field . It has 10 turns.
The emf induced is
(a) B a
2
 sin ?t
(b) B a
2
 cos ?t
(c) 5  B a
2
(d) 10 B a
2
 ? sin ?t
9. A conducting wire frame is placed in a magnetic
field which is directed into the paper. The magnetic
field is increasing at a constant rate. The directions
of induced current in wires AB and CD are
(a) B to A and D to C
(b) A to B and C to D
(c) A to B and D to C
(d) B to A and C to D
10. A square metal loop of side 10 cm and resistance 1 ? is moved with a
constant velocity partly inside a uniform magnetic field of 2 Wbm
–2
,
directed into the paper, as shown in the figure. The loop is connected to
Page 5


PART-I (Single Correct MCQs)
1. A metal rod of length l cuts across a uniform magnetic field B with a 
velocity v. If the resistance of the circuit of which the rod forms a part
is r, then the force required to move the rod is
(a)
(b)
(c)
(d)
2. Three solenoid coils of same dimension, same number of turns and
same number of layers of windings are taken. Coil 1 with inductance L
1
was wound using a Mn wire of resistance 11 ?/m, coil 2 with
inductance L
2
 was wound using the similar wire but the direction of
winding was reversed in each layer; coil 3 with inductance L
3
 was
wound using a superconducting wire. The self inductance of the coils
L
1
, L
2
,  L
3 
are
(a) L
1 
= L
2
= L
3
(b) L
1 
= L
2
;  L
3 
= 0
(c) L
1
= L
3
; L
2
= 0
(d) L
1 
> L
2 
> L
3
3. 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, . 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
(a) the circular and the elliptical loops.
(b) only the elliptical loop.
(c) any of the four loops.
(d) the rectangular, circular and elliptical loops.
4. A metal ring is held horizontally and bar magnet is dropped through the
ring with its length along the axis of the ring. The acceleration of the
falling magnet
(a) is equal to g
(b) is less than g
(c) is more than g
(d) depends on the diameter of ring and length of magnet
5. Which of the following figure correctly depicts the Lenz’s law. The
arrows show the movement of the labelled pole of a bar magnet into a
closed circular loop and the arrows on the circle show the direction of
the induced current
(a)
(b)
(c)
(d)
6. A metallic rod of length ‘ l’ is tied to a string of
length 2 l and made to rotate with angular speed
? on a horizontal table with one end of the string
fixed. If there is a vertical magnetic field ‘B’ in
the region, the e.m.f. induced across the ends of
the rod is
(a)
(b)
(c)
(d)
7. Figure shows a conducting rod of negligible resistance that can slide on
smooth U-shaped rail made of wire of resistance 1?/m. Position of the
conducting rod at t = 0 is shown. A time t dependent magnetic field B =
2t tesla is switched on at t = 0.
At t = 0, when the magnetic field is switched  on, the conducting rod is
moved to the left at constant speed 5cm/s by some external means. The
rod moves perpendicular to the rails. At t = 2s, induced emf has
magnitude
(a) 0.12V
(b) 0.08V
(c) 0.04V
(d) 0.02 V
8. A square loop of side a is rotating about its
diagonal with angular velocity ? in a
perpendicular magnetic field . It has 10 turns.
The emf induced is
(a) B a
2
 sin ?t
(b) B a
2
 cos ?t
(c) 5  B a
2
(d) 10 B a
2
 ? sin ?t
9. A conducting wire frame is placed in a magnetic
field which is directed into the paper. The magnetic
field is increasing at a constant rate. The directions
of induced current in wires AB and CD are
(a) B to A and D to C
(b) A to B and C to D
(c) A to B and D to C
(d) B to A and C to D
10. A square metal loop of side 10 cm and resistance 1 ? is moved with a
constant velocity partly inside a uniform magnetic field of 2 Wbm
–2
,
directed into the paper, as shown in the figure. The loop is connected to
a network of five resistors each of value 3?. If a steady current of 1 mA
flows in the loop, then the speed of the loop is
(a) 0.5 cms
–1
(b) 1 cms
–1
(c) 2 cms
–1
(d) 4 cms
–1
11. The figure shows certain wire segments joined together
to form a coplanar loop. The loop is placed in a
perpendicular magnetic field in the direction going into
the plane of the figure.
The magnitude of the field increases with time. I
1
 and I
2
 are
the currents in the segments ab and cd. Then,     
(a) I
1 
> I
2
(b) I
1 
<  I
2
(c) I
1 
is in the direction ba and  I
2
 is in the direction cd
(d) I
1 
is in the direction ab and  I
2 
is in the direction dc
12. The mutual inductance of a pair of coils, each of N turns, is M henry. If
a current of I ampere in one of the coils is brought to zero in t second,
the emf induced per turn in the other coil, in volt, will be
(a) (b)  
(c)
(d)
13. 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