Electric Field and Potential Simulation
This interactive simulation demonstrates the concepts from Example 2.3, showing electric field lines and potential differences around point charges.
Simulation
Example 2.3 Questions
(a) Give the signs of the potential difference \( V_P - V_Q \); \( V_B - V_A \).
As \( V \propto \frac{1}{r} \), \( V_P > V_Q \). Thus, \((V_P - V_Q)\) is positive. Also \( V_B \) is less negative than \( V_A \). Thus, \( V_B > V_A \) or \((V_B - V_A)\) is positive.
(b) Give the sign of the potential energy difference of a small negative charge between the points Q and P; A and B.
A small negative charge will be attracted towards positive charge. The negative charge moves from higher potential energy to lower potential energy. Therefore the sign of potential energy difference of a small negative charge between Q and P is positive. Similarly, \((P.E.)_A > (P.E.)_B\) and hence sign of potential energy differences is positive.
(c) Give the sign of the work done by the field in moving a small positive charge from Q to P.
In moving a small positive charge from Q to P, work has to be done by an external agency against the electric field. Therefore, work done by the field is negative.
(d) Give the sign of the work done by the external agency in moving a small negative charge from B to A.
In moving a small negative charge from B to A work has to be done by the external agency. It is positive.
(e) Does the kinetic energy of a small negative charge increase or decrease in going from B to A?
Due to force of repulsion on the negative charge, velocity decreases and hence the kinetic energy decreases in going from B to A.
