PHY059 · Electrostatics · Class 12 + College
Electric potential
Objective: To understand electric potential around a point charge as a 'hill' (or valley) of energy per unit charge.
🧰 Apparatus
- (Simulation) point charge
- Equipotential mapping kit: conducting paper, electrodes, voltmeter
📐 Formulas and SI units
V = kq / r (V)
E = −dV/dr
💡 Theory
Electric potential is the work done per unit positive charge to bring it from far away: V = kq/r. A positive charge makes a potential hill and a negative charge a valley. Equipotentials are circles around a point charge, always at right angles to field lines.
🪜 Procedure
- Set up the conducting paper with electrodes and a low-voltage supply.
- Use the voltmeter probe to find points of equal voltage.
- Join them to draw equipotential lines.
- Compare with V = kq/r for a point charge in the simulation.
📋 Observations Simulated values
✅ Result and conclusion
1 nC gives 89.9 V at 0.1 m; the potential halves when the distance doubles (unlike E, which quarters).
🔬 In a real lab
Conducting paper is not uniform, so mapped lines wobble; meters load the paper slightly.
⚠️ Safety
Use only the low-voltage supply for mapping.
❓ Quick check
1. Potential falls with distance as…
2. Equipotentials and field lines meet at…
3. Unit of potential?
🏋️ Practice
Easyq = 2 nC, r = 0.2 m. V?
Answer: 89.9 V
MediumWork to move 1 µC across 100 V?
Answer: 100 µJ
ChallengePotential of a negative charge is…?
Answer: Negative