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) BRlv
(b) B²l²v²/R
(c) B l²v²/ R
(d) Blv/R
(b) B²l²v²/R
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 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
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
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 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 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 square of side L meters lies in the x-y plane in a region where the magnetic field is given by B = B₀ (2ˆi + 3ˆj + 4kˆ) Tesla, where B₀ is constant. The magnitude of flux passing through the square Is
(A) 2B₀L² Wb
(B) 3B₀L² Wb
(C) 4B₀L² Wb
(D) √(29) B₀L² Wb
Polaroid glasses is used in sun glasses because :
a. It reduces the light intensity to half on account of polarization
b. It is fashionable
c. It has good colour
d. It is cheaper
The angle of incidence at which reflected light is totally polarised for reflection from air to glass (refractive index n) is
In Young’s double slit experiment, using sodium light (λ = 5898) , 92 fringes are seen. If given colour (λ= 5461) is used, how many fringes will be seen?
I. 67
II. 95
III. 99
IV. 84
If the width of the slit in single slit diffraction experiment is doubled, then the central maximum of diffraction pattern becomes:
(A) broader and brighter
(B) broader and fainter
(C) sharper and fainter
(D) sharper and brighter
The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 A is of the order of
(a) 106 rad
(b) 10−2 rad
(c) 10−4 rad
(d) 10−6 rad
A wire in the form of a circular loop, of one turn carrying a current, produces magnetic induction B at the centre. If the same wire is looped into a coil of two turns and carries the same current, the new value of magnetic induction at the centre is-
a) B
b) 4B
c) 2B
d) 8B.
The figure below shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 Ω maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.04 V (for very moderate currents up to a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 KΩ is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf Ꜫ and the balance point, found similarly, turns out to be at 82.3 cm length of the wire. What is the value Ꜫ?
(a) 0.25 V
(b) 2.25 V
(c) 3.25 V
(d) 1.25 V