A hollow metal sphere of radius 5cm is charged such that the potential on its surface is 10 V. The potential at a distance of 2 cm from the centre of the sphere is

zero
10 V
4 V
10/3 V

Solution

Potential at any point inside the sphere = potential at the surface of the sphere = 10V.

An electron of mass m and charge e is accelerated from rest through a potential difference V in vacuum. Its final speed will be

\(\sqrt{\frac{2e\, V}{m}}\)
\(\sqrt{\frac{2e\, V}{m}}\)
e V/2m
e V/m

Solution

K.E. =Work done = eV

\(\frac{1}{2}m\: v^{2}=eV\: \: \: V=\sqrt{\frac{2eV}{m}}\)

The electric potential due to a small electric dipole at a large distance r from the centre of the dipole is proportional to

r
1/r
1/r²
1/r³

Solution

Due to small dipole, \(V\alpha \frac{1}{r^{2}}\).

Two conducting spheres of radii r₁ and r₂ are equally charged. The ratio of their potentials is

r₁/r₂
r₂/r₁
\(r_{1}^{2}/r_{2}^{2}\)
\(r_{2}^{2}/r_{1}^{2}\)

Solution

The positive terminal of 12 V battery is connected to the ground. Then the negative terminal will be at

– 6 V
+ 12 V
zero
– 12 V

Solution

When negative terminal is grounded, positive terminal of battery is at +12 V. When positive terminal is grounded, the negative terminal will beat –12 V.

The capacitance of a metallic sphere is 1μF, then it’s radius is nearly

1.11 m
10 m
9 km
1.11 cm

Eight drops of mercury of equal radius and possessing equal charge combine to form a big drop. The capacitance of bigger drop as compared to each small drop is

16 times
8 times
4 times
2 times

A sphere of radius R has uniform volume charge density.The electric potential at a points (r

due to the charge inside a sphere of radius r only
due to the entire charge of the sphere
due to the charge in the spherical sheel of inner and outer radii rand R, only
independent of r

Two identical conducting balls having positive charges q₁ and q₂ are separated by a distance r.If they are made to touch each other and then separated to the same distance,the force between them will be

less than before
same as before
more than before
zero

A parallel plate capacitor is charged to a certain voltage.Now,if the dielectric material (with dielectric constant k) is removed then the

capacitance increases by a factor of k
electric field reduces by a factor k
voltage across the capacitor decreases by a factor k
None of these

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