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
(a) 3.14 × 10⁻² V
(b) 3.14 × 10⁻³ V
(c) 6.28 × 10⁻² V
(d) 6.28 × 10⁻³ V
(b) 3.14 × 10⁻³ V
A conducting loop of area 5.0 cm² is placed in a magnetic field which varies sinusoidally with time as B=0.2 sin300t. The normal to the coil makes an angle of 60° with the field. The emf induced at t=(π/900)s
(a) 7.5 × 10⁻³ V
(b) Zero
(c) 15 × 10⁻³ V
(d) 20 × 10⁻³ V
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
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
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
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
To observe diffraction, the size of the obstacle
(a) should be X/2, where X is the wavelength.
(b) should be of the order of wavelength.
(c) has no relation to wavelength.
(d) should be much larger than the wavelength.
The phenomenon of diffraction can be treated as interference phenomenon if the number of coherent sources is:
(A) one
(B) two
(C) zero
(D) infinity
A glass rod acquires charge by rubbing it with silk cloth. The charge on glass rod is due to :
(A) Friction
(B) Conduction
(C) Induction
(D) Radiation
When interference of light takes place
(a) energy is created in the region of maximum intensity
(b) energy is destroyed in the region of maximum intensity
(c) conservation of energy holds good and energy is redistributed
(d) conservation of energy does not hold good
Which of the following is correct for light diverging from a point source?
(a) The intensity decreases in proportion with the distance squared.
(b) The wave front is parabolic.
(c) The intensity at the wavelength does not depend on the distance.
(d) None of these.
The V-i graph for a conductor at temperature T¹ and T² are as shown in the figure. (T² - T¹) is proportional to
(a) cos θ
(b) sin θ
(c) cot 2θ
(d) tan θ
\(10^6\) electrons are taken out of a pith ball. The positive charges on the pith ball is
A. 1.6x \(10^{-13}\) C
B. 1.6x \(10^{-19}\) C
C. 1.6x \(10^{-25}\) C
D. none of these