A charge of 10 e.s.u. is placed at a distance of 2 cm from a charge of 40 e.s.u. and 4 cm from another charge of 20 e.s.u. The potential energy of the charge 10 e.s.u. is: (in ergs)
1. | 87.5 | 2. | 112.5 |
3. | 150 | 4. | 250 |
In a certain charge distribution, all points having zero potential can be joined by a circle S. Points inside S have positive potential, and points outside S have a negative potential. A positive charge, which is free to move, is placed inside S. What is the correct statement about S:
1. | It will remain in equilibrium | 2. | It can move inside S, but it cannot cross S |
3. | It must cross S at some time | 4. | It may move, but will ultimately return to its starting point |
Two charges q1 and q2 are placed 30 cm apart, as shown in the figure. A third charge q3 is moved along the arc of a circle of radius 40 cm from C to D. The change in the potential energy of the system is , where k is:
1. | 8q2 | 2. | 8q1 |
3 | 6q2 | 4. | 6q1 |
If the dielectric constant and dielectric strength be denoted by k and x respectively, then a material suitable for use as a dielectric in a capacitor must have:
1. high k and high x.
2. high k and low x.
3. low k and low x.
4. low k and high x.
Three capacitors of capacitances 3 μF, 9 μF and 18 μF are connected once in series and another time in parallel. The ratio of equivalent capacitance in the two cases will be:
1. 1 : 15
2. 15 : 1
3. 1 : 1
4. 1 : 3
Four capacitors each of capacity 3 μF are connected as shown in the adjoining figure. The ratio of equivalent capacitance between A and B and between A and C will be:
1. 4: 3
2. 3: 4
3. 2: 3
4. 3: 2
A parallel plate condenser is filled with two dielectrics as shown. Area of each plate is A metre2 and the separation is t metre. The dielectric constants are k1 and k2 respectively. Its capacitance in farad will be:
1.
2.
3.
4.
In the connections shown in the adjoining figure, the equivalent capacity between A and B will be:
1. 10.8 μF
2. 69 μF
3. 15 μF
4. 10 μF
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). |
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% |