The direction of induced emf during electromagnetic induction is given by
(a) Faraday’s law
(b) Lenz’s law
(c) Maxwell’s law
(d) Ampere’s law
There is a 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,
(a) Current is induced in the loop in the anti-clockwise direction
(b) Current is induced in the loop in clockwise direction
(c) AC Current is induced in the loop
(d) No current is induced in the loop
A coil of N turns and mean cross-sectional area A is rotating with uniform angular velocity ω about an axis at right angle to uniform magnetic field B. The induced emf in the coil will be
(a) NBAsinωt
(b) NBωsinωt
(c) NB/Asinωt
(d) NBAωsinωt
The SI unit of inductance is the henry. It can be written as
(a) weber/ampere
(b) volt-second/ampere
(c) joul/(ampere)²
(d) ohm-second
The self inductance of long solenoid cannot be increased by
(a) increasing its area of cross section
(b) increasing its length
(c) changing the medium with grater permeability
(d) Increasing the current through it.
Two currents loops are concentric and lie in the same plane. The current in the outer loop is anti clockwise and increasing with time. The induced current in the inner loop ,is
(a) Clockwise
(b) Zero
(c) Counter-clockwise
(d) None of these
A long solenoid has 2000 turns. When a current of 2 A flows through it, then the magnetic flux linked with each turn of the solenoid is 2 × 10⁻³ Wb. The self inductance of the solenoid is
(a) 1 H
(b) 2 H
(c) 3 H
(d) 4 H
A conducting rod of unit length moves with a velocity 10 m/s in a direction perpendicular to its length and perpendicular to a uniform magnetic field of magnitude 0.2 T. The emf induced between the ends of the rod is
(a) 4 V
(b) 2V
(c) 1V
(d) Zero
A coil of wire of certain radius has 500 turns and self inductance of 75 mH. The self inductance of a second similar coil of 600 turns will be
(a) 100 mH
(b) 150mH
(c) 108 mH
(d) 105mH
In a circuit with a coil of resistance 3Ω, the magnetic flux changes from 1.0 Wb to 10.0 Wb in 0.3 s. The charge that flows in the coil during this time is
(a) 2.0 C
(b) 3.0 C
(c) 4.0 C
(d) 1.0 C
A square loop of side l , resistance R is placed in a uniform magnetic field B acting normally to the plane of the loop. If we attempt to pull it out of the field with a constant velocity v , then the power needed is
(a) BRlv
(b) B²l²v²/R
(c) B l²v²/ R
(d) Blv/R
The magnetic flux linked with a coil is given by the equation Ø = 2t² + 2t + 4 weber. The magnitude of induced emf at time t=2s will be
(a) 16 V
(b) 10V
(c) 12V
(d) 8V
A vertical disc of radius 10 cm makes 10 revolutions per second about a horizontal axis passing through its centre. A uniform magnetic field 10⁻² T acts perpendicular to the plane of the disc. The potential difference between its centre and rim in volts is
(a) 3.14 × 10⁻² V
(b) 3.14 × 10⁻³ V
(c) 6.28 × 10⁻² V
(d) 6.28 × 10⁻³ V
The following figure shows the top view of a rod that can slide without friction. The resistance is 5.0Ω and a 2.5 T magnetic field is directed perpendicularly downwards into the paper. Length of the rod is 1.0 m.