Electric Potential & Equipotentials
Explore electric potential (voltage) as the electric potential energy per unit charge, measured in volts. Calculate potential from point charges using V = kQ/r and understand that equipotential lines connect points of equal potential, always perpendicular to electric field lines. Visualize how positive charges move from high to low potential (downhill), work is done moving charges against the field, and the relationship ΔV = -∫E·ds connects potential difference to electric field.
WHAT IS ELECTRIC POTENTIAL?
Electric potential (or voltage) is the amount of electric potential energy per unit charge at a point in an electric field. Unlike the electric field, which is a vector, electric potential is a **scalar quantity**. It tells you how much work is required to move a unit charge from a reference point (usually infinity) to that location. For a point charge, the potential is proportional to the charge and inversely proportional to the distance .
EQUIPOTENTIAL LINES
Equipotential lines represent locations where the electric potential is constant. No work is required to move a charge along an equipotential line. Crucially, **equipotential lines are always perpendicular to electric field lines**. In a uniform field, equipotential lines are equally spaced parallel planes.
HOW TO USE THIS VISUALIZATION
1. **Visualize the Landscape**: Think of electric potential as height on a hill. Positive charges are peaks, and negative charges are valleys. 2. **Map Equipotentials**: Use the probe to find points of equal voltage and draw the contour lines. 3. **Compare with Fields**: Toggle field lines to see how they always cross equipotentials at 90°.
CORE FORMULAS
AP EXAM CONNECTION
Unit: Unit 3: Electric Force, Field, and Potential (Topic 3.3)
Learning Objective: PVFE-1.B
COMMON MISCONCEPTIONS
- Confusing potential (V) with potential energy (U).
- Thinking potential is a vector (it has no direction, only magnitude).
- Thinking work is done moving along an equipotential line.
KEY TAKEAWAYS
- Potential is energy per charge (Volts).
- Equipotentials are perpendicular to field lines.
- Positive charges create potential "peaks"; negative charges create "valleys".
PRACTICE QUESTIONS
Q1 (CONCEPTUAL): Does the electric potential increase or decrease as you move in the direction of an electric field line?
Show Answer & Explanation
Answer: Decrease
Explanation: Electric field lines point from higher potential to lower potential (downhill).
Q2 (QUANTITATIVE): How much work is required to move a 2C charge across a potential difference of 5V?
Show Answer & Explanation
Answer: 10 J
Explanation: .
