A wooden stick of length 3l is rotated about an end with constant angular velocity w in a uniform magnetic field B perpendicular to the plane of motion. If the upper one third of its length in coated with copper, the potential difference across the copper coating of the stick is

The resistance of each straight section is r. Find the equivalent resistance between A and B.

PQ is an infinite current carrying conductor. AB and CD are smooth conducting rods on which a conductor EF moves with constant velocity V as shown. The force needed to maintain constant speed of EF is.

When a galvanometer is shunted with a 4 Ω resistance, the deflection is reduced to one-fifth. If the galvanometer is further shunted with a 2 Ω wire, the further reduction in the deflection will be (the main current remains the same).

Figure shows a system of three concentric metal shells A, B and C with radii a, 2a and 3a respectively. Shell B is earthed and shell C is given a charge Q. Now if shell C is connected to shell A, then the final charge on the shell B, is equal to :

Two small pith balls, each carrying a charge q are attached to the ends of a light rod of length d, which is  suspended from the ceiling by a thin torsion free fiber as shown in figure. There is a uniform magnetic field B pointing straight down, in the cylindrical region of radius R around the fiber. The system is initially at rest. If the magnetic field is turned off. Which of the following happen to the system -

In a practical wheat stone bridge circuit as shown, when one more resistance of 100 ? is connected in parallel with unknown resistance ' x ', then ratio l₁ / l₂ becomes '2'. l₁ is balance length. AB is a uniform wire. Then value of ' x ' must be :

The work function of a metal is 1 eV. When the surface of this metal is illuminated with light of wavelength 64000 Å, then the maximum kinetic energy of emitted photoelectron will be

If K₁ and K₂ are maximum kinetic energies of photoelectrons emitted when lights of wavelength λ₁and λ₂ respectively incident on a metallic surface and λ₁ = 3λ₂ then