1. The number of electrons that must be removed from an electrically neutral silver dollar to give it a charge of +2.4C is
2. Three charges +Q, q,+Q are placed respectively at distance 0, d/2 and d from the origin on the X-axis. If the net force experienced by +Q placed at x=0 is zero, then value of q is
3. Two field lines can never cross each other because
4. When an electric dipole P is placed in a uniform electric field E, then at what angle between P and E the value of torque will be maximum?
5. The figure given below shows various equipotential surfaces.
6. An electric dipole, made up of positive and negative charges each of 3.5 µC and placed at a distance 4.2 cm apart is placed in an electric field of~5.87 x 105 NC-1. What will be the maximum torque which the field can exert on the dipole? Also, obtain the work that must be done to turn the dipole from 0° to 180°.
7. When Pis normal to the surface, the polarisation is numerically equal to the
8. van de graaff generator is based on the phenomenon of corona discharge, which is used for developing
9. The temperature dependence of resistances of Cu and undoped Si in the temperature range 300-400 K, is best described by
10. An electric motor operating on a 50 V DC supply draws a current of 12 A. If the efficiency of the motor is 30%, then estimate the resistance of the windings of the motor.
11. Find VpVo in the circuit shown in figure
12. The maximum power dissipated in an external resistance R when connected to a cell of emf E and internal resistance r will be
13. A straight wire of mass 200 g and length 1.5 m carries a current of 2 A. It is held in mid-air by a uniform horizontal magnetic field. What is the magnitude of magnetic field?
14. Cyclotron frequency of an electron circulating in a magnetic field of 1T is
15. A toroid of core of inner radius 0.25 m and outer radius 0.26 m around which 3500 turns of a wire are wound. If the current in the wire is 11 A, then magnetic field inside the core of the toroid is
16. The magnetic moment of an electron orbiting in a circular orbit of radius r with a speed v is equal to
17. The length of a magnetised steel wire is I and the magnetic moment is m. It is bent into the shape of L with two equal sides. The magnetic moment now will be
18. The core of a toroid having 3000 turns has inner and outer radii 11 cm and 12 cm, respectively. The magnetic field in the core for a current of 0.70 A is 2.5 T. The relative permeability of the core is
19. A square loop of side 10 cm and resistance 0.5 2 is placed vertically in the east-west plane. A uniform magnetic field of 0.10 T is set-up across the plane in the north-east direction. The magnetic field is decreased to zero in 0.70 s at a steady rate. The magnitudes of induced emf and current during this time interval are
20. An inductance of negligible resistance, whose reactance is 120 2 at 200 Hz is connected to a 240 V, 60 Hz, power line. The current in the inductor is
