JEE Questions for Physics Electromagnetic Induction Quiz 8 - MCQExams.com

A step up transformer connected to a 220 V AC line is to supply 22 kV for a neon sign in secondary circuit. In primary circuit a fuse wire is connected which is to blow when the current in the secondary circuit exceeds 10 mA. The turn ratio of the transformer is
  • 50
  • 100
  • 150
  • 200
A transformer is used to
  • Change the alternating potential
  • Change the alternating current
  • To prevent the power loss in alternating current flow
  • To increase the power of current source
A step-up transformer operates on a 230 V line and supplies a load of 2 A. The ratio of the primary and secondary windings is 1: 25. The current in the primary is
  • 15 A
  • 50 A
  • 25 A
  • 12.5 A
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
  • 200 V, 50 Hz
  • 2 V, 50 Hz
  • 200 V, 500 Hz
  • 2 V, 5 Hz
A step-down transformer is connected to main supply 200 V to operate a 6V, 30W bulb. The current in primary is
  • 0.3 A
  • 3 A
  • 1.5 A
  • 0.15 A
The number of turns in primary and secondary coils of a transformer are 100 and 20 respectively. If an alternating potential of 200 volt is applied to the primary, the induced potential in secondary, will be
  • 10 V
  • 40 V
  • 1000 V
  • 20,000 V
The ratio of secondary to primary turns is 9 : 4. If power input is P, what will be the ratio of power output (neglect all losses) to power input
  • 4 : 9
  • 9 : 4
  • 5 : 4
  • 1 : 1
Voltage in the secondary coil of a transformer does not depend upon
  • Voltage in the primary coil
  • Ratio of number of turns in the two coils
  • Frequency of the source
  • Both (a) and (b)
In a step-up transformer the turn ratio is 1 : 10. A resistance of 200 ohm connected across the secondary is drawing a current of 0.5 A. What is the primary voltage and current?
  • 50 V, 1 A
  • 10 V, 5 A
  • 25 V, 4 A
  • 20 V, 2 A
Large transformers, when used for sometime, become hot and are cooled by circulating oil. The heating of transformer is due to
  • Heating effect of current alone
  • Hysteresis loss alone
  • Both the hysteresis loss and heating effect of current
  • None of the above
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 500 V output will be
  • 100
  • 200
  • 400
  • 300
An ideal transformer has 500 and 5000 turn in primary and secondary windings respectively. If the primary voltage is connected to a 6 V battery then the secondary voltage is
  • 0
  • 60 V
  • 0.6 V
  • 6.0 V
In a primary coil 5 A current is flowing on 220 volts. In the secondary coil 2200 V voltage produces. Then ratio of number of turns in secondary coil and primary coil will be
  • 1 : 10
  • 10 : 1
  • 1 : 1
  • 11 : 1
A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80% the current drawn from the line is
  • 3 A
  • 30 A
  • 0.3 A
  • 2.4 A
The output voltage of a transformer connected to 220 volt line is 1100 volt at 2 A current. Its efficiency is 100%. The current coming from the line is
  • 20 A
  • 10 A
  • 11 A
  • 22 A
In a region of uniform magnetic induction B =10–2 tesla, a circular coil of radius 30 cm and resistance π2 ohm is rotated about an axis which is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is
  • 4 π2 mA
  • 30 mA
  • 6 mA
  • 200 mA
The number of turns of the primary and the secondary coils of a transformer are 10 and 100 respectively. The primary voltage and the current are given as 2 V and 1 A. Assuming the efficiency of the transformer as 90%, the secondary voltage and the current respectively are
  • 20 V and 0.1 A
  • 0.2 V and 1 A
  • 20 V and 0.09 A
  • 0.2 V and 0.9 A
In an ideal transformer the number of turns of primary and secondary coil is given as 100 and 300 respectively. If the power input is 60 W, the power output is
  • 100 W
  • 300 W
  • 180 W
  • 60 W
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
  • 1/2 Bω l2
  • 3/4 B ω l2
  • B ω l2
  • 2B ω l2
In the circuit shown below, the key K is closed at t = 0. The current through the battery is
Physics-Electromagnetic Induction-69021.png

  • Physics-Electromagnetic Induction-69022.png
  • 2)
    Physics-Electromagnetic Induction-69023.png

  • Physics-Electromagnetic Induction-69024.png

  • Physics-Electromagnetic Induction-69025.png
An e.m.f. of 15 volt is applied in a circuit containing 5 henry inductance and 10 ohm resistance. The ratio of the currents at time t = ∞ and at t =1 second is

  • Physics-Electromagnetic Induction-69027.png
  • 2)
    Physics-Electromagnetic Induction-69028.png

  • Physics-Electromagnetic Induction-69029.png

  • Physics-Electromagnetic Induction-69030.png
A thin semicircular conducting ring of radius R is falling with its plane vertical in a horizontal induction B. At the position MNQ, the speed of the ring is V and the potential difference developed across the ring is
Physics-Electromagnetic Induction-69032.png
  • Zero
  • B vπR2 / 2 and M is at higher potential
  • πRBV and Q is at higher potential
  • 2RBV and Q is at higher potential
Two identical coaxial circular loops carry current i each circulating in the clockwise direction. If the loops are approaching each other, then
  • Current in each loop increases
  • Current in each loop remains the same
  • Current in each loop decreases
  • Current in one-loop increases and in the other it decreases
At a place the value of horizontal component of the earth\'s magnetic field H is 3 × 10–5 weber / m2. A metallic rod AB of length 2 m placed in east-west direction, having the end A towards east, falls vertically downward with a constant velocity of 50 m/s. Which end of the rod becomes positively charged and what is the value of induced potential difference between the two ends?
  • End A, 3 × 10–3 mV
  • End A, 3 mV
  • End B, 3 × 10–3 mV
  • End B, 3 mV
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
Physics-Electromagnetic Induction-69035.png
  • Increase
  • Remain the same
  • Decrease
  • Increase or decrease depending on whether the semicircle bulge is towards the resistance or away from it
A circular loop of radius R carrying current I lies in x – y plane with its centre at origin. The total magnetic flux through x – y plane is
  • Directly proportional to I
  • Directly proportional to R
  • Directly proportional to R2
  • Zero
Two identical circular loops of metal wire are lying on a table without touching each other. Loop–A carries a current which increases with time. In response, the loop–B.
  • Remains stationary
  • Is attracted by the loop–A
  • Is repelled by the loop–A
  • Rotates about its CM ,with CM fixed (CM is the centre of mass)
A small square loop of wire of side l is placed inside a large square loop of wire of side L (L > l). The loops are coplanar and their centres coincide. The mutual inductance of the system is proportional to
  • l / L
  • l2 / L
  • L / l
  • L2 / l
A wire of length 1 m is moving at a speed of 2ms–1 perpendicular to its length and in a homogeneous magnetic field of 0.5 T. The ends of the wire are joined to a circuit of resistance 6 Ω. The rate at which work is being done to keep the wire moving at constant speed is

  • Physics-Electromagnetic Induction-69037.png
  • 2)
    Physics-Electromagnetic Induction-69038.png

  • Physics-Electromagnetic Induction-69039.png
  • 1W
A uniform but time-varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region
Physics-Electromagnetic Induction-69041.png
  • Is zero
  • Decreases as 1/r
  • Increases as r

  • Physics-Electromagnetic Induction-69042.png
A coil of wire having finite inductance and resistance has a conducting ring placed coaxially within it. The coil is connected to a battery at time t = 0, so that a time-dependent current I1 (t) starts flowing through the coil. If I2(t) is the current induced in the ring and B(t) is the magnetic field at the axis of the coil due to I1 (t), then as a function of time (t > 0), the product I2(t) B(t)
  • Increases with time
  • Decreases with time
  • Does not vary with time
  • Passes through a maximum
Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be
Physics-Electromagnetic Induction-69045.png
  • Maximum in situation (A)
  • Maximum in situation (B)
  • Maximum in situation (C)
  • The same in all situations
A metallic square loop ABCD is moving in its own plane with velocity v in a uniform magnetic field perpendicular to its plane as shown in the figure. An electric field is induced
Physics-Electromagnetic Induction-69046.png
  • In AD, but not in BC
  • In BC, but not in AD
  • Neither in AD nor in BC
  • In both AD and BC

Physics-Electromagnetic Induction-69047.png

  • Physics-Electromagnetic Induction-69048.png
  • 2)
    Physics-Electromagnetic Induction-69049.png

  • Physics-Electromagnetic Induction-69050.png
  • Zero
As shown in the figure, P and Q are two coaxial conducting loops separated by some distance. When the switch S is closed, a clockwise current Ip flows in P (as seen by E) and an induced current IQ1 flows in Q.
The switch remains closed for a long time. When S is opened, a current IQ2 flows in Q. Then the directions of IQ1 and IQ2 (as seen by E) are
Physics-Electromagnetic Induction-69052.png
  • Respectively clockwise and anticlockwise
  • Both clockwise
  • Both anticlockwise
  • Respectively anticlockwise and clockwise
A short-circuited coil is placed in a time-varying magnetic field. Electrical power is dissipated due to the current induced in the coil. If the number of turns were to be quadrupled and the wire radius halved, the electrical power dissipated would be
  • Halved
  • The same
  • Doubled
  • Quadrupled
A physicist works in a laboratory where the magnetic field is 2T. She wears a necklace enclosing area 0.01 m2 in such a way that the plane of the necklace is normal to the field and is having a resistance R = 0.01 Ω. Because of power failure, the field decays to 1T in time 10–3 seconds. Then what is the total heat produced in her necklace? (T = tesla)
  • 10 J
  • 20 J
  • 30 J
  • 40 J
A coil of inductance 8.4 mH and resistance 6 Ω is connected to a 12 V battery. The current in the coil is 1.0 A in the time (approx.)
  • 500 sec
  • 20 sec
  • 35 milli sec
  • 1 milli sec
As shown in the figure a metal rod makes contact and completes the circuit. The circuit is perpendicular to the magnetic field with B = 0.15 tesla. If the resistance is 3 Ω force needed to move the rod as indicated with a constant speed of 2m / sec is
Physics-Electromagnetic Induction-69057.png
  • 3.75 × 10–3 N
  • 3.75 × 10–2 N
  • 3.75 × 102 N
  • 3.75 × 10–4 N

Physics-Electromagnetic Induction-69235.png
  • (ec = ed) < (ea = eb)
  • (ec = ed) > (ea = eb)
  • ec > ed > eb > ea
  • ec < ed < eb < ea
In the following figure, the magnet is moved towards the coil with a speed v and induced e.m.f. If magnet and coil recede away from one another each moving with speed v, the induced e.m.f. in the coil will be
Physics-Electromagnetic Induction-69059.png
  • e
  • 2e
  • e / 2
  • 4e
A current carrying solenoid is approaching a conducting loop as shown in the figure. The direction of induced current as observed by an observer on the other side of the loop will be
Physics-Electromagnetic Induction-69061.png
  • Anticlockwise
  • Clockwise
  • East
  • West
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
Physics-Electromagnetic Induction-69063.png
  • B to A and D to C
  • A to B and C to D
  • A to B and D to C
  • B to A and C to D
A square metallic wire loop of side 0.1 m and resistance of 1 Ω is moved with a constant velocity in a magnetic field of 2 wb/m2 as shown in figure. The magnetic field is perpendicular to the plane of the loop, loop is connected to a network of resistances. What should be the velocity of loop so as to have a steady current of lmA in loop
Physics-Electromagnetic Induction-69065.png
  • 1 cm / sec
  • 2 cm / sec
  • 3 cm / sec
  • 4 cm / sec
A conductor ABOCD moves along its bisector with a velocity of 1 m/s through a perpendicular magnetic field of 1 wb/m2, as shown in fig. If all the four sides are of lm length each, then the induced e.m.f. between points A and D is
Physics-Electromagnetic Induction-69067.png
  • 0
  • 1.41 volt
  • 0.71 volt
  • None of these
A conducting rod PQ of length L = 1.0 m is moving with a uniform speed v = 2 m/s in a uniform magnetic field B = 4.0T directed into the paper. A capacitor of capacity C = 10 µF is connected as shown in figure. Then
Physics-Electromagnetic Induction-69069.png

  • Physics-Electromagnetic Induction-69070.png
  • 2)
    Physics-Electromagnetic Induction-69071.png

  • Physics-Electromagnetic Induction-69072.png
  • Charge stored in the capacitor increases exponentially with time
The resistance in the following circuit is increased at a particular instant. At this instant the value of resistance is 10 Ω. The current in the circuit will be
Physics-Electromagnetic Induction-69074.png

  • Physics-Electromagnetic Induction-69075.png
  • 2)
    Physics-Electromagnetic Induction-69076.png

  • Physics-Electromagnetic Induction-69077.png

  • Physics-Electromagnetic Induction-69078.png
Shown in the figure is a circular loop of radius r and resistance R. A variable magnetic field of induction B = B0 e–t is established inside to coil. If the key (K) is closed, the electrical power developed right after closing the switch is equal to
Physics-Electromagnetic Induction-69080.png

  • Physics-Electromagnetic Induction-69081.png
  • 2)
    Physics-Electromagnetic Induction-69082.png

  • Physics-Electromagnetic Induction-69083.png

  • Physics-Electromagnetic Induction-69084.png
A conducting ring is placed around the core of an electromagnet as shown in fig. When key K is pressed, the ring
Physics-Electromagnetic Induction-69086.png
  • Remain stationary
  • Is attracted towards the electromagnet
  • Jumps out of the core
  • None of the above
The north and south poles of two identical magnets approach a coil, containing a condenser, with equal speeds from opposite sides. Then
Physics-Electromagnetic Induction-69087.png
  • Plate 1 will be negative and plate 2 positive
  • Plate 1 will be positive and plate 2 negative
  • Both the plates will be positive
  • Both the plates will be negative
0:0:1


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