MEDIUM
Earn 100

What is a spherical capacitor? Derive an expression for the capacitance of spherical capacitor.

Important Questions on Electrostatics

MEDIUM
A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system
HARD

A capacitor of μF is charged as shown in the diagram. When the switch S is turned to position 2, the percentage of its stored energy dissipated is

Question Image

HARD

Two identical parallel plate capacitors of capacitance each are connected in series with a battery of emf, E as shown. If one of the capacitors is now filled with a dielectric of dielectric constant k, the amount of charge which will flow through the battery is (neglect internal resistance of the battery)

Question Image

HARD
A parallel plate capacitor of capacitance C has spacing d between two plates having area A. The region between the plates is filled with N dielectric layers, parallel to its plates, each with thickness δ=dN. The dielectric constant of the mth layer is Km=K1+mN. For a very large N>103, the capacitance C is αK0Adln2. The value of α will be____.

[0 is the permittivity of free space]
EASY
A parallel plate capacitor with plates of area 1 m2 each, are at a separation of 0.1 m. If the electric field between the plates is 100 N C-1, the magnitude of charge on each plate is: (Takeε0=8.85×1012 C2 N-1 m-2)
HARD

A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm and with a dielectric of dielectric constant 2.2 between them. When the electric field in the dielectric is 3 × 1 0 4  V/m , the charge density of the positive plate will be close to :

MEDIUM

An electron enters a parallel plate capacitor with horizontal speed μ and is found to deflect by angle θ on leaving the capacitor as shown. It is found that tanθ=0.4 and gravity is negligible.

Question Image
If the initial horizontal speed is doubled, then tanθ will be:

HARD
A capacitor is made of two square plates each of side a making a very small angle α between them, as shown in figure. The capacitance will be close to:
Question Image
EASY

In the figure is shown a system of four capacitors connected across a 10 V battery. The charge that will flow from switch S when it is closed is:
Question Image

HARD
A parallel plate air capacitor of capacitance C is connected to a cell of emf V and then disconnected from it. A dielectric slab of dielectric constant K, which can just fill the air gap of the capacitor, is now inserted in it. Which of the following is incorrect?
EASY
A parallel plate capacitor has 1μF capacitance. One of its two plates is given +2μC charge and the other plate, +4 μC charge. The potential difference developed across the capacitor is:
EASY
A parallel plate capacitor is of area 6 cm2 and a separation 3 mm. The gap is filled with three dielectric materials of equal thickness (see figure) with dielectric constant K1=10, K2=12 and K3=14. The dielectric constant of a material which when fully inserted in above capacitor, gives same capacitance would be:

Question Image
MEDIUM
In the given circuit, the charge on 4μF capacitor will be:
Question Image
HARD

What are the charges stored in the 1 μF and 2 μF capacitors in the circuit below, once the currents become steady?

Question Image

MEDIUM
In a parallel plate air capacitor the distance between plates is reduced to one fourth and the space between them is filled with a dielectric medium of constant 2. If the initial capacity of the capacitor is 4 μF. Then its new capacity is
MEDIUM
A capacitor of capacitance C charged by an amount Q is connected in parallel with an uncharged capacitor of capacitance 2C. The final charges on the capacitors are
HARD
Question Image
A parallel plate capacitor has plates of area A separated by distance d between them. It is filled with a dielectric which has a dielectric constant that varies as Kx=K01+αx where x is the distance measured from one of the plates. If αd<<1, the total capacitance of the system is best given by the expression:
EASY
Two identical conducting spheres A and B carry an equal charges. They are separated by a distance much larger than their diameters, and the force between them is F. A third identical conducting sphere, C, is uncharged. Sphere C is first touched to A, then to B, and then removed. As a result, the force between A and B would be equal to:
MEDIUM
Two capacitors C1 and C2 are charged to 120 V and 200 V respectively. It is found that by connecting them together the potential on each one can be made zero. Then:
EASY
The charge on a capacitor plate in a circuit, as a function of time, is shown in the figure:
Question Image
What is the value of current at t=4 s?