Q.1- A point charge +q is placed at a distance d from an isolated conducting plane. The field at a point P on the other side of the plane is:
(a) directed perpendicular to the plane and away from the plane.
(b) directed perpendicular to the plane but towards the plane.
(c) directed radially away from the point charge.
(d) directed radially towards the point charge.
Q.2- The Electric field at a point is:
(a) always continuous.
(b) continuous if there is no charge at that point.
(c) discontinuous only if there is a negative charge at that point.
(d) discontinuous if there is a charge at that point.
Q.3- A positively charged particle is released from rest in an uniform electric field. The electric potential energy of the charge:
(a) remains a constant because the electric held is uniform.
(b) increases because the charge moves along the electric field.
(c) decreases because the charge moves along the electric field.
(d) decreases because the charge moves opposite to the electric field.
Q.4- Equipotential surfaces:
(a) are closer in regions of large electric fields compared to regions of lower electric fields.
(b) will be more crowded near sharp edges of a conductor.
(c) will be more crowded near regions of large charge densities.
(d) will always be equally spaced.
Q.5- Two heater wires of equal length are first connected in series and then in parallel. The ratio of heat produced in the two cases is:
Q.6- The length of a given cylindrical wire is increased by 100%. Due to the consequent decreases in diameter the change in the resistance of the wire will be___
Q.7- The radius of curvature of the path of the charged particle in a uniform magnetic field is directly proportional to____
(a) the charge on the particle
(b) the momentum of the particle
(c) the energy of the particle
(d) the intensity of the field
Q.8- A charge moves in a circle perpendicular to a magnetic field. The time period of revolution is independent of:
(a) magnetic field
(c) mass of the particle
(d) velocity of the particle
Q.9- An incident ray strikes a plane mirror at an angle of 15° with the mirror. The angle between the incident ray and reflected ray is:
(d) none of these
Q.10- For an object at infinity, a concave mirror produces an image at its focus which is:
(d) real, inverted and diminished
Q.11- The rate of radiation of a black body at 0°C is E J/s. The rate of radiation of this black body at 273°C will be:
Q.12- The simple Bohr model cannot be directly applied to calculate the energy levels of an atom with many electrons. This is because:
(a) of the electrons not being subject to a central force.
(b) of the electrons colliding with each other
(c) of screening effects
(d) the force between the nucleus and an electron will no longer be given by Coulomb’s law.
Q.13- Two H atoms in the ground state collide inelastically. The maximum amount by which their combined kinetic energy is reduced is:
(a) 10.20 eV
(b) 20.40 eV
(c) 13.6 eV
(d) 27.2 eV
Q.14- The conductivity of a semiconductor increases with increase in temperature because:
(a) number density of free current carriers increases.
(b) relaxation time increases.
(c) both number density of carriers and relaxation time increase.
(d) number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density.
Q.15- When an electric field is applied across a semiconductor:
(a) electrons move from lower energy level to higher energy level in the conduction band.
(b) electrons move from higher energy level to lower energy level in the conduction band.
(c) holes in the valence band move from higher energy level to lower energy level.
(d) holes in the valence band move from lower energy level to higher energy level.