The magnetic flux through a circuit of resistance R changes by an amount Δφ in time Δt, Then the total quantity of electric charge Q, which passing during this time through any point of the circuit is given by
Q=ΔϕΔt
Q=ΔϕΔt×R
Q=−ΔϕΔt+R
Q=ΔϕR
A coil of resistance 20Ω and inductance 5H has been connected to a 200 V battery. The maximum energy stored in the coil is
250 J
125 J
500 J
100 J
Lenz's law is a consequence of the law of conservation of
Charge
Momentum
Mass
Energy
If all linear dimensions of an inductor are tripled, then self-inductance will become (keeping the total number of turns per unit length constant)
3 times
9 times
27 times
1/3 times
A metallic ring is attached to the wall of a room. When the north pole of a magnet is brought near to it, the induced current in the ring will be:
first clockwise and then anticlockwise.
in the clockwise direction.
in the anticlockwise direction.
first anticlockwisand then clockwise.
A coil having an area A0 is placed in a magnetic field which changes from B0 to 4B0 in a time interval t. The e.m.f. induced in the coil will be
3A0B0t
4A0B0t
3B0A0t
4B0A0t
A copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet while it is passing through the ring is-
Equal to that due to gravity
Less than that due to gravity
More than that due to gravity
Depends on the diameter of the ring and the length of the magnet
A magnet is brought towards a coil (i) speedily (ii) slowly then the induced e.m.f./induced charge will be respectively
More in first case / More in the first case
More in first case/Equal in both case
Less in first case/More in second case
Less in first case/Equal in both case
As shown in the figure, a magnet is moved with a fast speed towards a coil at rest. Due to this induced electromotive force, induced current and induced charge in the coil is E, I, and Q respectively. If the speed of the magnet is doubled, the incorrect statement is
E increases
I increases
Q remains the same
Q increases
A coil having 500 square loops each of the side 10 cm is placed normal to a magnetic field which increases at the rate of 1.0 tesla/second. The induced e.m.f. in volts is
0.1
0.5
1
5
When a magnet is pushed in and out of a circular coil C connected to a very sensitive galvanometer G as shown in the adjoining diagram with a frequency v, then
Constant deflection is observed in the galvanometer
Visible small oscillations will be observed in the galvanometer if v is about 50 Hz
Oscillations in the deflection will be observed clearly if v = 1 or 2 Hz
No variation in the deflection will be seen if v = 1 or 2 Hz
The magnetic field in a coil of 100 turns and 40 square cm area is increased from 1 Tesla to 6 Tesla in 2 second. The magnetic field is perpendicular to the coil. The e.m.f. generated in it is
104 V
1.2 V
1.0 V
10–2 V
A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in the horizontal direction so that the pendulum now swings through the field, the pendulum will
Keep oscillating with the old-time period
Keep oscillating with a smaller time period
Keep oscillating with a larger time period
Come to rest very soon
In a circuit with a coil of resistance 2 ohms, the magnetic flux changes from 2.0 Wb to 10.0 Wb in 0.2 second. The charge that flows in the coil during this time is
5.0 coulomb
4.0 coulomb
1.0 coulomb
0.8 coulomb
The total charge induced in a conducting loop when it is moved in the magnetic field depends on
The rate of change of magnetic flux
Initial magnetic flux only
The total change in magnetic flux
Final magnetic flux only
An aluminum ring B faces an electromagnet A. The current I through A can be altered. Then :
Whether I increases or decreases, B will not experience any force
If I decrease, A will repel B
If I increases, A will attract B
If I increases, A will repel B
A coil having n turns and resistance RΩ is connected with a galvanometer of resistance 4RΩ. This combination is moved in time t seconds from a magnetic field W1 weber/m2 to W2 weber/m2. The induced current in the circuit is: (Assume area = 1m2)
−W2−W15 Rnt
−n(W2−W1)5 Rt
−(W2−W1)Rnt
−n(W2−W1)Rt
A rectangular coil ABCD is rotated anticlockwise with a uniform angular velocity about the axis shown in the diagram below. The axis of rotation of the coil as well as the magnetic field B are horizontal. The induced e.m.f. in the coil would be maximum when
The plane of the coil is horizontal
The plane of the coil makes an angle of 45° with the magnetic field
The plane of the coil is at right angles to the magnetic field
The plane of the coil makes an angle of 30° with the magnetic field
An electric potential difference will be induced between the ends of the conductor shown in the diagram when the conductor moves in the direction
P
Q
L
M
Two rails of a railway track insulated from each other and the ground are connected to a milli voltmeter. What is the reading of voltmeter, when a train travels with a speed of 180 km/hr along the track. Given that the vertical component of earth's magnetic field is 0.2 × 10–4 weber/m2 and the rails are separated by 1 metre
10–2 volt
10–4 volt
10–3 volt
1 volt
A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A magnetic induction B constant in time and space, pointing perpendicular and into the plane of the loop exists everywhere. The current induced in the loop is
BlvR clockwise
A conducting wire is moving towards right in a magnetic field B. The direction of induced current in the wire is shown in the figure. The direction of magnetic field will be
In the plane of paper pointing towards right
In the plane of paper pointing towards left
Perpendicular to the plane of paper and down wards
Perpendicular to the plane of paper and upwards
One conducting U tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed v then the emf induced in the circuit in terms of B, l and v where l is the width of each tube, will be
Zero
2 Blv
Blv
– Blv
The magnitude of the earth’s magnetic field at a place is B0 and the angle of dip is δ. A horizontal conductor of length l lying along the magnetic north-south moves eastwards with a velocity v. The emf induced across the conductor is
B0lv sinδ
B0lv
B0lv cosδ
Two circuits have coefficient of mutual induction of 0.09 henry. Average e.m.f. induced in the secondary by a change of current from 0 to 20 ampere in 0.006 second in the primary will be
120 V
80 V
200 V
300 V
A coil and a bulb are connected in series with a dc source, a soft iron core is then inserted in the coil. Then
Intensity of the bulb remains the same
Intensity of the bulb decreases
Intensity of the bulb increases
The bulb ceases to glow
The inductance of a coil is 60μH. A current in this coil increases from 1.0 A to 1.5 A in 0.1 second. The magnitude of the induced e.m.f. is
60 × 10–6 V
300 × 10–4 V
30 × 10–4 V
3 × 10–4 V
The self inductance of a coil is L. Keeping the length and area same, the number of turns in the coil is increased to four times. The self inductance of the coil will now be
14L
4 L
16 L
A coil has an inductance of 2.5 H and a resistance of 0.5 r. If the coil is suddenly connected across a 6.0 volt battery, then the time required for the current to rise 0.63 of its final value is
3.5 sec
4.0 sec
4.5 sec
5.0 sec
Pure inductance of 3.0 H is connected as shown below. The equivalent inductance of the circuit is
1 H
2 H
3 H
9 H
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