Q. No.The force between two small charged spheres having charges of \(2\times 10^{-7}\) C and \(3\times 10^{-7}\) C placed \(30\) cm apart in the air is:
1. \(6 \times 10^{-3}~ \mathrm{N}\)
2. \(5 \times 10^{-3}~ \mathrm{N}\)
3. \(4 \times 10^{-4}~ \mathrm{N}\)
4. \(5 \times 10^{-4}~ \mathrm{N}\)
The electrostatic force on a small sphere of charge 0.4 µC due to another small sphere of charge –0.8 µC in the air is 0.2 N. The distance between the two spheres is:
1. 14 cm
2. 12 cm
3. 16 cm
4. 10 cm
Four point charges qA = 2μc, qB = -5μc, qC = 2μc and qD = -5μc are located at corners of a square ABCD of side 10 cm. The force on a charge of 1μc placed at the center of the square is:
1. 2 N
2. 1 N
3. 5 N
4. 0 N
Two point charges qA = 3 µC and qB= –3 µC are located 20 cm apart in a vacuum. The electric field at the midpoint O of the line AB joining the two charges is:
1. 4.5×106 N/C along OA
2. 5.4×106 N/C along OA
3. 4.5×106 N/C along OB
4. 5.4×106 N/C along OB
A system has two charges, \(q_\mathrm{A} = 2.5 \times 10^{-7}~\text{C}\) and \(q_\mathrm{B} = -2.5 \times 10^{-7}~\text{C}\), is located at points \(\mathrm{A}\): \((0,0,-15~\text{cm})\) and \(\mathrm{B}\): \((0,0,+15~\text{cm})\) respectively. The electric dipole moment of the system is:
| 1. | \(7.5\times 10^{-8}~\text{C-m}~(\text{along negative z-axis})\) |
| 2. | \(8.5\times 10^{-8}~\text{C-m}~(\text{along positive z-axis})\) |
| 3. | \(5.5\times 10^{-8}~\text{C-m}~(\text{along positive z-axis})\) |
| 4. | \(3.5\times 10^{-8}~\text{C-m}~(\text{along negative z-axis})\) |
An electric dipole with dipole moment is aligned at 30° with the direction of a uniform electric field of magnitude The magnitude of the torque acting on the dipole is:
1. 2 × 10−5 N m
2. 10−4 N m
3. 10−5 N m
4. 2 × 10−4 N m
Which of the following statements about electric field lines (due to static charges) is incorrect?
| 1. | electric field lines never cross each other at any point. |
| 2. | electric field lines do not form any closed loop. |
| 3. | electric field lines can not be taken as continuous curves. |
| 4. | electric field lines start from a positive charge and end on a negative charge. |
A polythene piece rubbed with wool is found to have a negative charge of . Transfer of mass from wool to polythene is:
1. 0.7 × 10 - 18 kg
2. 1.7 × 10 - 17 kg
3. 0.7 × 10 - 17 kg
4. 1.7 × 10 - 18 kg
Two insulated charged copper spheres A and B have their centers separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is ? The radii of A and B are negligible compared to the distance of separation.
1. 1.52 × 10−2 N
2. 3.7 × 10−2 N
3. 2.01 × 10−2 N
4. 2.23 × 10−1 N
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