A metallic sphere of capacitance , charged to electric potential is connected by a metal wire to another metallic sphere of capacitance charged to electric potential . The amount of heat produced in connecting the wire during the process is:
1.
2.
3.
4. zero
Four equal charges Q are placed at the four corners of a square of each side is ‘a’. Work done in removing a charge – Q from its centre to infinity is
(1) 0
(2)
(3)
(4)
Two spheres of radius a and b respectively are charged and joined by a wire. The ratio of the electric field at the surface of the spheres is
(1) a/b
(2) b/a
(3) a2/b2
(4) b2/a2
An electron of mass m and charge e is accelerated from rest through a potential difference V in vacuum. The final speed of the electron will be
(1)
(2)
(3)
(4)
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 the resulting system
1. increases by a factor of 4
2.decreases by a factor of 2
3. remain the same
4. increases by a factor of 2
The diagrams below show regions of equipotentials.
A positive charge is moved from A to B in each diagram. Then:
1. | the maximum work is required to move q in figure(iii). |
2. | in all four cases, the work done is the same. |
3. | the minimum work is required to move q in the figure(i). |
4. | the maximum work is required to move q in figure(ii). |
An electric dipole is place at an angle of \(30^{\circ}\) with an electric field intensity \(2\times10^{5}~\text{N/C}\). It experiences a torque equal to \(4~\text{Nm}\). The charge on the dipole, if the dipole length is \(2~\text{cm}\), is:
1. | \(8~\text{mC}\) | 2. | \(2~\text{mC}\) |
3. | \(5~\text{mC}\) | 4. | \(7~\mu\text{C}\) |
A parallel-plate capacitor of area A, plate separation d, and capacitance C is filled with four dielectric materials having dielectric constants and as shown in the figure below. If a single dielectric material is to be used to have the same capacitance C in this capacitor, then its dielectric constant k is given by
(a)
(b)
(c)
(d)
A capacitor of 2 is charged as shown in the figure. When the switch S is turned to position 2, the percentage of its stored energy dissipated is:
1. | 20% | 2. | 75% |
3. | 80% | 4. | 0% |
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?
1. | The potential difference between the plates decreases K times |
2. | The energy stored in the capacitor decreases K times |
3. | The change in energy stored is \({1 \over 2} CV^{2}(\frac{1}{K}-1)\) |
4. | The charge on the capacitor is not conserved |