Figures (a) and (b) show the field lines of a positive and negative point charge respectively.
The signs of the potential difference
Figures (a) and (b) show the field lines of a positive and negative point charge respectively. The signs of the potential energy difference of a small negative charge between the points Q and P & A and B are respectively:
Figures (a) and (b) show the field lines of a positive and negative point charge respectively. The sign of the work done by the field in moving a small positive charge from Q to P and the sign of the work done by the external agency in moving a small negative charge from B to A, respectively, will be:
Figures (a) and (b) show the field lines of a positive and negative point charge respectively. The kinetic energy of a small negative charge in going from B to A:
1. decreases.
2. increases.
3. remains the same.
4. first increases and then decreases.
Four charges are arranged at the corners of a square ABCD of side d, as shown in the figure. The work required to put together this arrangement will be:
Four charges are arranged at the corners of a square ABCD of side d, as shown in the figure. A charge is brought from to the centre E of the square, the four charges being held fixed at its corners. How much work is needed to do this?
The electrostatic potential energy of a system consisting of two charges 7 µC and –2 µC (and with no external field) placed at (–9 cm, 0, 0) and (9 cm, 0, 0) respectively is:
1. 0.2 J
2. -0.7 J
3. -0.2 J
4. 0.7 J
How much work is required to separate two charges 7 µC and –2 µC (and with no external field) placed at (–9 cm, 0, 0) and (9 cm, 0, 0) infinitely away from each other?
1. 0.2 J
2. -0.7 J
3. -0.2 J
4. 0.7 J
The electrostatic potential energy of a system consisting of two charges 7 µC and –2 µC (in an external electric field E = A(1/r2); A = 9 × 105 C m–2) placed at (–9 cm, 0, 0) and (9 cm, 0, 0) respectively is:
1. 34 J
2. 49.3 J
3. 47 J
4. 43 J
A molecule of a substance has a permanent electric dipole moment of magnitude 10–29 C m. A mole of this substance is polarised (at low temperature) by applying a strong electrostatic field of magnitude 106 V m–1. The direction of the field is suddenly changed by an angle of . The heat released by the substance in aligning its dipoles along the new direction of the field is: (For simplicity, assume 100% polarisation of the sample).
1. 6 J
2. 8 J
3. 3 J
4. 4 J