JEE Questions for Physics Electromagnetic Induction Quiz 3 - MCQExams.com

If rotational velocity of a dynamo armature is doubled, then induced emf will become... What is increased in step down transformer ?
  • Half
  • Two times
  • Four times
  • unchanged
The core of a transformer is laminated so that.......
  • Ratio of I/p & O/p voltage increases
  • Rusting of core may be stopped
  • Energy loss due to eddy current may be reduced
  • Change in flux is increased
In transformer, core is made of soft iron to reduce.....
  • Hysterlsis losses
  • Eddy current losses
  • Force opposing current
  • the weight
An ideal transformer has 1:25 turn ratio. The peak value of the ac is 28 V. The rms ms secondary voltage is nearest to......
  • 50 V
  • 70 V
  • 100 V
  • 40 V
A primary winding of transformer has 500 turns whereas its secondary has 5000 turns. Primary is connected to ac supply of 20V, 50Hz The secondary output of....
  • 200V, 25 Hz
  • 200 V, 50Hz
  • 2 V, 100 Hz
  • 2V, 50 Hz
A step down transformer is connected to main supply 200 V to operate a 6V, 30 w bulb. The current in primary is.....
  • 3A
  • 1.5 A
  • 0.3 A
  • 0.15 A
Alternating current can not be measured by dc ammeter because,
  • ac can not pass through dc ammeter
  • Average value of complete cycle is zero
  • ac is virtual
  • ac changes its direction
The resistance of a coil for dc is in ohms. In ac, the resistance
  • will remain same
  • will increase
  • will decrease
  • will be zero
An alternating current of rms value 10 A is passed through a 12Ω resistance. The maximum potential difference across the resistor is,
  • 20 V
  • 90 V
  • 169. 68 V
  • None of these
220 V, 50 Hz, ac is applied to a resistor. The instantaneous value of voltage is

  • Physics-Electromagnetic Induction-68656.png
  • 220sin100πt

  • Physics-Electromagnetic Induction-68657.png
  • 220sin50πt
General in an alternating current circuit.
  • The average value of current is 20w
  • The average value of square of current is zero
  • Average power dissipation is zero
  • The phase difference between voltage and current is zero
In the transmission of a.c. power through transmission lines, when the voltage is shaped up n times, the power loss in transmission,
  • increase n times
  • Decrease n times
  • Increase n2 times
  • Decrease n2 times
An alternating voltage is represented as E = 20 sin300t. The average value of voltage over one cycle will be.
  • zero
  • 10 volt

  • Physics-Electromagnetic Induction-68658.png

  • Physics-Electromagnetic Induction-68659.png
An ac source is rated at 220V, 50 Hz. The time taken for voltage to change from its peak value to zero is,
  • 50 sec
  • 0.02 sec
  • 5 sec
  • 5 × 10–3 sec
The instantaneous voltage through a device of impedance 20Ω is ε = 80 sin100πt . The effective value of the current is,
  • 3A
  • 2.828 A
  • 1.732 A
  • 4A
A choke coil has.
  • High inductance and low resistance
  • Low inductance and high resistance
  • High inductance and high resistance
  • Low inductance and low resistance
A 20 volts ac is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 V, the voltage across the coil is,
  • 16 volts
  • 10 volts
  • 8 volts
  • 6 volts
The impedance of a circuit consists of 3Ω resistance and 4Ω reactance. The power factor of the circuit is.
  • 0.4
  • 0.6
  • 0.8
  • 1.0
A coil of inductance L has an inductive reactance of XL in an AC circuit in which the effective current is I. The coil is made from a super-conducting material and has no resistance. The rate at which power is dissipated in the coil is.
  • 0
  • IXL
  • I2XL

  • Physics-Electromagnetic Induction-68660.png
Two identical incandescent light bulbs are connected as shown in figure. when the circuit is an AC voltage source of frequency f, which of the following observations will be correct.
Physics-Electromagnetic Induction-68661.png
  • both bulbs will glow alternatively
  • 2)
    Physics-Electromagnetic Induction-68662.png
  • Bulb b1 will light up initially and goes off, bulb b2 will be ON constantly.
  • Bulb b1 will blink and bulb b2 will be ON constantly.
For high frequency, a capacitor offers
  • More reactance
  • Less reactance
  • Zero reactance
  • Infinite reactance
The coil of a choke in a circuit
  • increase the current
  • Decrease the current
  • Does not change the current
  • Has high resistance to bc circuit
In a LCR circuit capacitance is changed from C to 2C. For the resonant fequency to remain unchanged, the inductance should be change from L to
  • 4L
  • 2L
  • L/2
  • L/4
In an LCR series ac circuit the voltage across each of the components L, C and R is 50 V. The voltage across the LC combination will be
  • 50 V
  • 50√2 V
  • 100 V
  • 0 V (zero)
A metallic rod of length l is tied to a string of length 2l and made to rotate with angular speed co on a horizontal table with one end of the string fixed. If there is a vertical magnetic field B in the region, the emf induced across the ends of the rod is
Physics-Electromagnetic Induction-68663.png

  • Physics-Electromagnetic Induction-68664.png
  • 2)
    Physics-Electromagnetic Induction-68665.png

  • Physics-Electromagnetic Induction-68666.png

  • Physics-Electromagnetic Induction-68667.png
In the following figure, the variation of electric field magnitude E versus time is shown for four uniform electric fields contained within identical circular regions. Arrange the fields according to the magnitudes of the magnetic fields, they induce at the edge of the region, in decreasing order
Physics-Electromagnetic Induction-68669.png
  • P, R , Q , S
  • R , P, Q , S
  • Q , R , P , S
  • S , P , Q , R
A current carrying infinitely long wire is kept along the diameter of a circular wire loop, without touching it. The correct statement (s) is (are)
  • the emf induced in the loop is zero, if the current is constant
  • the emf induced in the loop is finite, if the current is constant
  • the emf induced in the loop is zero, if the current decreases at a steady rate
  • the emf induced in the loop is finite, if the current decreases at a steady rate
Flux ϕ (in weber) in a closed circuit of resistance 20 Ω varies with time t (in sec) according to equation ϕ =6t2 - 5t + 1.
The magnitude of the induced current at t = 0.25 s is
  • 1.2 A
  • 0.8 A
  • 0.6 A
  • 0.1 A
There is an uniform magnetic field directed perpendicular and into the plane of the paper. An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper. Then,
  • current is induced in the loop in the anti-clockwise direction
  • current is induced in the loop in the clockwise direction
  • AC is induced in the loop
  • no current is induced in the loop
A rectangular loop of sides 10 cm and 5 cm with a cut is stationary between the pole pieces of an electromagnet. The magnetic field of the magnet is normal to the loop. The current feeding the electromagnet is reduced, so that the field decreased from its initial value of 0.3 T at the rate of 0.02 Ω. If the cut is joined and the loop has a resitance of 2.0 Ω, the power dissipated by the loop as heat is
  • 5 nW
  • 4 nW
  • 3 nW
  • 2 nW
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. I1 and I2 are the currents in the segments ab and cd. Then,
Physics-Electromagnetic Induction-68673.png
  • I1 > I2
  • I1 < I2
  • I1 is in the direction ba and I2 is in the direction cd
  • I1 is in the direction ab and I2 is in the direction dr
when a circular coil of radius 1 m and 100 turns is rotated in a horizontal uniform magnetic field, the peak value of emf induced is 100 V. The coil is unwound and then rewound into a circular coil of radius 2 m. If it is rotated now, with the same speed, under similar conditions, the new peak value of emf developed is
  • 50 V
  • 25 V
  • 100 V
  • 150 V
  • 200 V

Physics-Electromagnetic Induction-68675.png

  • Physics-Electromagnetic Induction-68676.png
  • 2)
    Physics-Electromagnetic Induction-68677.png

  • Physics-Electromagnetic Induction-68678.png

  • Physics-Electromagnetic Induction-68679.png
The time constant of a LR circuit is 20 ms The circuit is connected at t = 0 and the steady state current is found to be 4A. Find the current at 80 ms.
  • 0.98 A
  • 1 A
  • 0.44 A
  • 0.88 A
A rectangular coil ABCD which is rotated at a constant angular velocity about an horizontal as shown in the figure. The axis of rotation of the coil as well as the magnetic field B are horizontal, Maximum current will flow in the circuit, when the plane of the coil is
Physics-Electromagnetic Induction-68681.png
  • inclined at 30° to the magnetic field
  • perpendicular to the magnetic field
  • inclined at 45° to the magnetic field
  • parallel to the magnetic field
A circular coil of diameter 21 cm is placed in a magnetic field of induction 10-4 T. The magnitude of flux linked with coil, when the plane of coil makes an angle 30° with the field is
  • 1.44 × 10-6 Wb
  • 1.732 × 10-6 Wb
  • 3.1 × 10-6 Wb
  • 4.2 × 10-6 Wb
When a low flying aircraft passes over head, we sometimes notice a slight shaking of the picture on our TV screen. This is due to
  • diffraction of the signal received from the antenna
  • interference of the direct signal received by the antenna with the weak signal reflected by the passing aircraft
  • change of magnetic flux occuring due to the passage of aircraft
  • vibration created by the passage of aircraft
A magnet N-S is suspended from a spring and when it oscillates, the magnet moves in and out of the coil C. The coil is connected to a galvanometer G. Then, as the magnet oscillates,
Physics-Electromagnetic Induction-68684.png
  • G shows no deflection
  • G shows deflection to the left and right but the amplitude steadily decreases
  • G shows deflection to the left and right with constant amplitude
  • G shows deflection on one side
Two parallel rails of a railways track insulated from each other and with the ground are connected to a millivoltmeter. The distance between the rails is 1 m A train is travelling with a velocity of 72 km-h-1 along the track. The reading of the millivoltmeter (in mV) is (Vertical component of the earth's magnetic induction is 2 × 10-5 T)
  • 1.44
  • 0.72
  • 0.4
  • 0.2
O is the centre of two coplanar concentric circular conductors, A and B of radii r and R respectively as shown in the figure. Here, r <<< R. The mutual inductance of the system of the conductors can be given by
Physics-Electromagnetic Induction-68686.png

  • Physics-Electromagnetic Induction-68687.png
  • 2)
    Physics-Electromagnetic Induction-68688.png

  • Physics-Electromagnetic Induction-68689.png

  • Physics-Electromagnetic Induction-68690.png
Three solenoid coils of same dimension, same number of turns and same number of layers of winding are taken. Coil 1 with inductance L1 was wound using a Mn wire of resistance 11 Ωm-1, coil 2 with inductance L2 was wound using the similar wire but the direction of winding was reversed in each layer, coil 3 with inductance L3 was wound using a superconducting wire. The self inductance of the coils L1, L2 and L3 are
  • L1 = L2 = L3
  • L1 = L2 , L3 = 0
  • L1 = L3, L2 = 0
  • L1 > L2 > L3

Physics-Electromagnetic Induction-68693.png

  • Physics-Electromagnetic Induction-68694.png
  • 2)
    Physics-Electromagnetic Induction-68695.png

  • Physics-Electromagnetic Induction-68696.png

  • Physics-Electromagnetic Induction-68697.png
A solenoid of 1.5 m long with inner diameter of 4 cm has three layers of winding of 1000 turns each & carries a current of 2 A. The magnetic flux through a cross section of the solenoid is nearly.....

  • Physics-Electromagnetic Induction-68698.png
  • 2)
    Physics-Electromagnetic Induction-68699.png

  • Physics-Electromagnetic Induction-68700.png

  • Physics-Electromagnetic Induction-68701.png
A coil has an area of 0.05 m2 & it has 800 turns. It is placed perpendicularly in a magnetic field of strength, 4 x 10–5 Wb/m–2. It is rotated through 90o in 0.1 sec. The average emf induced in the coil is...
  • 0.056 v
  • 0.046 v
  • 0.026 v
  • 0.016 v
A bar magnet is moving along the common axis of two coils A &B towards A. current is induced in
Physics-Electromagnetic Induction-68702.png
  • Only A
  • Only B
  • both A& B in same direction
  • both A & B in opposite direction
A coil having n turns & resistance RΩ is connected with a galvanometer of resistance 4RΩ. This combination is moved from a magnetic field W1 Wb to W2 Wb in t second. The induced current in the circuit is....

  • Physics-Electromagnetic Induction-68703.png
  • 2)
    Physics-Electromagnetic Induction-68704.png

  • Physics-Electromagnetic Induction-68705.png

  • Physics-Electromagnetic Induction-68706.png

Physics-Electromagnetic Induction-68707.png
  • Increases
  • Decreased
  • Remain same
  • Depending on whether the semicircle bulge is towards the resistance or away from it
Two co – axial solenoids are made by a pipe of cross sectional area 10 cm2 and length 20 cm If one of the solenoid has 300 turns and the other 400 turns, their mutual inductance is........

  • Physics-Electromagnetic Induction-68708.png
  • 2)
    Physics-Electromagnetic Induction-68709.png

  • Physics-Electromagnetic Induction-68710.png

  • Physics-Electromagnetic Induction-68711.png
In circular coil. when no. of turns is doubled & resistance becomes half of the initial then inductance becomes....
  • 4 times
  • 2 times
  • 8 times
  • No change
When the switch S turned off.
Physics-Electromagnetic Induction-68713.png
  • Both B1 and B2 die out promptly
  • Both B1 and B2 die out with some delay
  • B1 dies out promptly but B2 with some delay
  • B2 dies out promptly but B1 with some delay
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Physics Quiz Questions and Answers