Key relationship
V=kq/r; W=qprobe ΔV; E=−dV/dr.
Physics · Class 12
Equipotential surfaces
All points at one radius from a point charge have the same potential. Move between spherical surfaces to change potential; travel along one surface requires zero electrostatic work.
Open the interactive experiment →Equipotential surfaces
ஒத்த ஆரத்தில் உள்ள புள்ளிகள் சமமின்னழுத்தம் உடையவை. சமமின்னழுத்தப் பரப்பில் வேலை பூஜ்யம்.
Key notes, relationships and model limits
Remember
All points at one radius from a point charge have the same potential. Move between spherical surfaces to change potential; travel along one surface requires zero electrostatic work.
Common trap
No work is required along an equipotential for the ideal electrostatic field; crossing equipotentials generally changes energy.
Model limits
A stationary point charge in vacuum produces spherical equipotentials, with zero potential chosen at infinity. This radial model does not describe an arbitrary charge distribution.
What you will learn
Use the controls and plotted relation to explain equipotential surfaces.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
For q=2 µC, every point on the r=1 m sphere has V≈17,975 V.
Why this matters
The model connects equipotential surfaces with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Moving a charge along one equipotential surface requires how much electrostatic work?
- q times the local field magnitude.
- Zero, because the potential difference is zero.
- q times the distance travelled, regardless of path.
Read the explanation
Zero, because the potential difference is zero.
Course connection: Class XII Chapter 2. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.