Physics · Electrostatic Potential

A test charge \( q \) is moved slowly from a point R to a point P against a repulsive electrostatic force due to a source charge \( Q > 0 \). If the work done by the external force is \( W_{RP} \), the potential energy difference \( \Delta U = U_P - U_R \) is given by:

1. A
   \( W_{RP} \)
2. B
   \( -W_{RP} \)
3. C
   \( \frac{W_{RP}}{q} \)
4. D
   \( -\frac{W_{RP}}{q} \)