Explanation:
Equipotential surface
→ P.D difference between two points on the surface is zero always since potential is same everywhere in equipotential surface.
→ The EF is always perpendicular to the surface because there is no potential gradient along any direction parallel to the surface P so no EF parallel to the surface
→ Equipotential surface can have any shape not just sphere.
→ No work is done in moving a charge along the surface, because potential difference is zero.
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A sphere of radius 1 cm has potential of 8000 V, then energy density near its surface will be
|
(a) 64 |
(b) 8 |
(b) 8 |
(d) 2.83 |
According to Bohr's theory, the expressions for the kinetic and potential energy of an electron revolving in an orbit is given respectively by
|
(a) + |
(b) + |
|
(c) |
(d) + |
Light waves producing interference have their amplitudes in the ratio 3 : 2. The intensity ratio of maximum and minimum of interference fringes is
|
(a) 36 : 1 |
(b) 9 : 4 |
(c) 25 : 1 |
(d) 6 : 4 |
A parallel plate capacitor is charged and the charging battery is then disconnected. If the plates of the capacitor are moved further apart by means of insulating handles, then
|
(a) The charge on the capacitor increases |
|
(b) The voltage across the plates decreases |
|
(c) The capacitance increases |
|
(d) The electrostatic energy stored in the capacitor increases |
When a piece of a ferromagnetic substance is put in a uniform magnetic field, the flux density inside it is four times the flux density away from the piece. The magnetic permeability of the material is
|
(a) 1 |
(b) 2 |
(c) 3 |
(d) 4 |
A small coil C with N = 200 turns is mounted on one end of a balance beam and introduced between the poles of an electromagnet as shown in figure. The cross sectional area of coil is A= 1.0 cm2, length of arm OA of the balance beam is l = 30 cm. When there is no current in the coil the balance is in equilibrium. On passing a current I = 22 mA through the coil the equilibrium is restored by putting the additional counter weight of mass ∆m = 60 mg on the balance pan. Find the magnetic induction at the spot where coil is located.
|
(a) 0.4 T |
(b) 0.3 T |
(c) 0.2 T |
(d) 0.1 T |
A short sighted person can see distinctly only those objects which lie between 10 cm and 100 cm from him. The power of the spectacle lens required to see a distant object is
|
(a) + 0.5 D |
(b) – 1.0 D |
(c) – 10 D |
(d) + 4.0 D |
Two small conducting spheres of equal radius have charges +10Μc and -20 μC respectively and placed at a distance R from each other experience force 
. If they are brought in contact and separated to the same distance, they experience force 
. The ratio of to is
|
(a) 1 : 8 |
(b) – 8 : 1 |
(c) 1 : 2 |
(d) – 2 : 1 |
Mixed 
and 
ions (mass of 
and that of 
beam passes a region of constant perpendicular magnetic field. If kinetic energy of all the ions is same then
|
(a) |
|
(b) |
|
(c) All the ions will be deflected equally |
|
(d) No ions will be deflected |
