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 spherical conductor of radius \(12~\text{cm}\) has a charge of \(1.6\times10^{-7}~\text{C}\) distributed uniformly on its surface. The electric field just outside the sphere is:
1. \(\text{zero}\)
2. \(10^5~ \text{NC}^{-1} \)
3. \(10^{-5}~ \text{NC}^{-1} \)
4. \(10^{6 }~ \text{NC}^{-1} \)
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 \(4\times 10^{-9}~\text{Cm}\) is aligned at \(30^{\circ}\) with the direction of a uniform electric field of magnitude \(5\times 10^{4}~\text{NC}^{-1}\). The magnitude of the torque acting on the dipole is:
1. \(2\times 10^{-5}~\text{N-m}\)
2. \(10^{-4}~\text{N-m}\)
3. \(10^{-5}~\text{N-m}\)
4. \(2\times 10^{-4}~\text{N-m}\)
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 \(3 \times10^{-7}~\text{C}\). Transfer of mass from wool to polythene is:
1. \(0.7\times10^{-18}~\text{kg}\)
2. \(1.7\times10^{-17}~\text{kg}\)
3. \(0.7\times10^{-17}~\text{kg}\)
4. \(1.7\times10^{-18}~\text{kg}\)
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
The figure below shows tracks of three charged particles in a uniform electrostatic field. Which particle has the highest charge to the mass ratio?
1. 2
2. 3
3. 1
4. 1 and 3
What is the flux of electric field through a square of 10 cm on a side whose plane is parallel to the y z – plane?
1. \(15\ N\ m^{2}/C\)
2.\(10\ N\ m^{2}/C\)
3.\(30 \ N\ m^{2}/C\)
4.0
The electric field at the surface of a black box indicates that the net outward flux through the surface of the box is \(8.0\times10^{3}\) N-m2/C. What is the net charge inside the box?
1. \(1.01\) \(\mu\)C
2. \(0.01\) \(\mu\)C
3. \(0.03\) \(\mu\)C
4. \(0.07\) \(\mu\)C