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Mere Teacher · Previous Year Questions
JEE Main Physics · Electromagnetic Induction · Set 6 (Q151-180)
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151.
The magnetic flux linked with a coil (in Wb) is given by the equation φ=5t2+3t+16 The magnitude of induced emf in the coil at the fourth second will be [NEET 2020]
(1)33 V
(2)43 V
(3)108 V
(4)10 V
152.
The self induced emf of a coil is 25 volts. When the current in it is changed at uniform rate from 10A to 25A in 1s, the change in the energy of the inductance is:
(1)540 J
(2)740 J
(3)637.5 J
(4)437.5 J
153.
A straight line conductor of length 0.4m is moved with a speed of 7m/s perpendicular to a magnetic field of intensity 0.9Wb/m2. The induced e.m.f. across the conductor is
(1)5.04V
(2)25.2V
(3)1.26V
(4)2.52V
154.
A square loop of side 1 m and resistance 1Ω placed in a magnetic field of 0.5 T. If the plane of loop is perpendicular to the direction of magnetic field, the magnetic flux through the loop is [NEET 2022]
(1)0.5 Wb
(2)1 Wb
(3)zero Wb
(4)2 Wb
155.
A circular loop of radius 7 cm is placed in uniform magnetic field of 0.2 T directed perpendicular to plane of loop. The loop is converted into a square loop in 0.5 s. The EMF induced in the loop is ____ mV.
(1)13.2
(2)1.32
(3)8.25
(4)6.6
156.
An emf of 0. 08 V is induced in a metal rod of length 10 cm held normal to a uniform magnetic field of 0.4 T, when move with a velocity of:
(1)0.5ms−1
(2)20ms−1
(3)3.2ms−1
(4)2ms−1
157.
Two coils A and B have mutual inductance 0.008H. The current changes in the coil A, according to the equation I=Imsinωt, where Im=5Λ and ω=200πrads−1. The maximum value of the e.m.f. induced in the coil B in volt is
(1)4π
(2)8π
(3)10π
(4)16π
158.
A 800 turn coil of effective area 0.05 m2 is kept perpendicular to a magnetic field 5 × 10–5 T. When the plane of the coil is rotated by 90º around any of its coplanar axis in 0.1 s, the emf induced in the coil will be:
(1)0.02 V
(2)2 V
(3)0.2 V
(4)2 × 10–3V
159.
When a current ' i ' through a solenoid is increasing at a constant rate then the induced current is
(1)Constant and it will be in the direction of ' i '
(2)Constant and it will be in a direction opposite to the 'i'
(3)Increases with time and it will be in the direction of 'i'
(4)Increases with time and opposite to the direction of 'i'
160.
The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an A.C. supply of 20 V, 50 Hz. The secondary will have an output of
(1)2 V, 50 Hz
(2)2 V, 5 Hz
(3)200 V, 50 Hz
(4)200 V, 500 Hz
161.
A series L−R circuit is connected to a battery of emf V. If the circuit is switched on at t=0, then the time at which the energy stored in the inductor reaches (n1) times of its maximum value, is
(1)RLln(n−1n+1)
(2)RLln(n−1n)
(3)RLln(n+1n)
(4)RLln(nn−1)
162.
The current in a coil of inductance 0.2H changes from 5A to 2A in 0.5sec. The magnitude of the average induced emf in the coil is
(1)30V
(2)0.3V
(3)0.6V
(4)1.2V
163.
An ideal transformer converts 220V a.c. to 3.3kV a.c. to transmit a power of 4.4kW. If primary coil has 600 turns, then alternating current in secondary coil is
(1)31A
(2)34A
(3)35A
(4)37A
164.
Which of the following combinations should be selected for better tuning of an L−C−R circuit used for communication?
(1)R=20Ω,L=1.5H,C=35μF
(2)R=25Ω,L=2.5H,C=45μF
(3)R=15Ω,L=3.5H,C=30μF
(4)R=25Ω,L=1.5H,C=45μF
165.
A rectangular loop of length 2.5m and width 2m is placed at 60∘ to a magnetic field of 4T. The loop is removed from the field in 10 sec. The average emf induced in the loop during this time is
(1)−2V
(2)+2V
(3)+1V
(4)−1V
166.
Two cables of copper are of equal lengths. One of them has a single wire of area of cross‐section A, while other has 10 wires of cross‐sectional area A/10 each. Give their suitability for transporting A.C. and D.C.
(1)only multiple strands for A.C., either for D.C.
(2)only multiple strands for A.C., only single strand for D.C.
(3)only single strand for D.C., either for A.C.
(4)only single strand for A.C., either for D.C.
167.
A 10 m long horizontal wire extends from North East to South West. It is falling with a speed of 5.0ms−1, at right angles to the horizontal component of the earth's magnetic field, of 0.3×10−4Wb/m2. The value of the induced emf in wire is:
(1)1.5×10−3V
(2)1.1×10−3V
(3)2.5×10−3V
(4)0.3×10−3V
168.
A transformer is used to light a 100 W and 110 V lamp from 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately
(1)50%
(2)90%
(3)10%
(4)30%
169.
What is the value of inductance L for which the current is maximum in a series LCR circuit with C=10μF and ω=1000s−1?
(1)1mH
(2)cannot be calculated unless R is known
(3)10mH
(4)100 mH
170.
The shiny metal disk in the electric power meter (along type) rotates due to
(1)temperature change
(2)eddy currents
(3)an external motor
(4)pressure change
171.
A uniform magnetic field B is perpendicular to the plane of a circular loop of diameter 10cm formed from wire of diameter 2mm and resistivity 2×10−8Ωm. If a current of 11A is to be induced in the loop then the rate at which B is to be changed is
(1)2.8Ts−1
(2)1.4Ts−1
(3)3.2Ts−1
(4)2.4Ts−1
172.
Two coils P and Q are kept near each other. When no current flows through coil P and current increases in coil Q at the rate 10 A/s, the e.m.f. in coil P is 15mV. When coil Q carries no current and current of 1.8 A flows through coil P, the magnetic flux linked with the coil Q is
(1)1.4mWb
(2)2.2mWb
(3)2.7mWb
(4)2.9mWb
173.
A power transmission line feeds input power at 2300 V a step down transformer with its primary windings having 4000 turns. The output power is delivered at 230 V by the transformer. If the current in the primary of the transformer is 5A and its efficiency is 90%, the output current would be:
(1)50 A
(2)45A
(3)35 A
(4)25 A
174.
A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60º is W. Now the torque required to keep the magnet in this new position is:
(1)32W
(2)3W
(3)3W
(4)23W
175.
A very long solenoid of radius R is carrying current I(t)=kte−αt(k>0), as a function function of time (t≥0). counter clockwise current is taken to be positive. A circular conducting coil of radius 2R is placed in the equatorial plane of the solenoid and concentric with the solenoid. The current induced in the outer coil is correctly depicted, as a function of time, by:
(1)
(2)
(3)
(4)
176.
If flux is given as φ=3t2+4t+8. Then find the induced emf at t=2s
(1)16V
(2)12V
(3)8V
(4)4V
177.
The electric field intensity produced by the radiation coming from a 100W bulb at a distance of 3m is E. The electric field intensity produced by the radiation coming from 60W at the same distance is 5xE. Where the valueof x=
178.
An inductor of 0.5 mH, a capacitor of 20 μF and resistance of 20Ω are connected in series with a 220 V ac source. If the current is in phase with the emf, the amplitude of current of the circuit is xA. The value of x is –
179.
A coil of 200 turns and area 0.20m2 is rotated at half a revolution per second and is placed in uniform magnetic field of 0.01T perpendicular to axis of rotation of the coil. The maximum voltage generated in the coil is β2π volt. The value of β is____
180.
A circular conducting coil of radius 1m is being heated by the change of magnetic field B passing perpendicular to the plane in which the coil is laid. The resistance of the coil is 2μΩ. The magnetic field is slowly switched off such that its magnitude changes in time as B=π4×10−3T(1−100t). The energy dissipated by the coil before the magnetic field is switched off completely is E = mJ.
