From the figure find the capacitance of the capacitor?

If a unit positive charge is taken from one point to another over an equipotential surface, then

• work is done on the charge

• work is done by the charge

• work done is constant

• no work is done

213.

The outer sphere of a spherical air capacitor is earthed. For increasing its capacitance

• vacuum is created between two spheres

• dielectric material is filled between the two
  spheres

• the space between two spheres is increased

• the earthing of the outer sphere is removed

What is the area of the plates of a 3F parallel plate capacitor, if the separation between the plates is 5 mm?

• 1.694 × 10⁹ m²

• 4.529 × 10⁹ m²

• 9.281 × 10⁹ m²

• 12.981 × 10⁹ m²

A condenser of capacitance 6 µF was originally charged to 10 V. Now potential difference is made 20 V. The increase in potential energy is

• 3×10^-4 J

• 6×10^-4 J

• 9×10^-4 J

• 12×10^-4 J

A parallel plate air capacitor has a capacitance C. When it is half-filled with a dielectric of dielectric constant 5, the percentage increase in the capacitance will be

• 400%

• 66.6%

• 33.3%

• 200%

A gang capacitor is formed by interlocking a number of plates as shown in the figure.The distance between the consecutive plates is 0.885 cm and the overlapping area of the plates is 5 cm. The capacity of the unit is

• 1.06 pF

• 4 pF

• 6.36 pF

• 12.72 pF

Two identical capacitors each of capacitance 5 µF are charged to potentials 2 kV and 1 kV respectively. Their -ve ends are connected together. When the +ve ends are also connected together, the loss of energy of the system is

• 160 J

• Zero

• 5 J

• 1.25 J

The ratio of magnetic potentials due to a magnetic dipole in the 'end on position' to that in the 'broad side on position' for the same distance from it is

• zero

• infinite

• 1

• 2

A 30 µF capacitor is charged by a constant current of 30 mA. If the capacitor is initially uncharged, how long does it take for the potential difference to reach 400 V?

• 0.2 s

• 0.4 s

• 0.6 s

• 0.8 s