Electric Potential (V)
Learning Outcomes
• Define electric potential and potential
difference
• Derive expressions for electric potential
• Relate electric field and potential
• Solve numerical problems
Electric Potential
• Electric potential at a point:
• Work done per unit positive charge in bringing
from infinity to a point.
• Scalar quantity
• Unit: volt (V)
• Electric potential at infinity is considered to be
zero.
Electric Potential Due to Uniform
Electric Field
• V = Ed (for uniform field)
• Field lines perpendicular to equipotentials
Electric Potential Difference
• Work done in moving unit charge between
two points
•
V = W/q
Electric Potential Energy
• U = qV
• Change in potential energy ΔU = qΔV
Equipotential Surfaces
• Surface of constant potential
• No work done moving charge along surface
Electric Potential Due to Point Charge
• V = kQ/r
• Depends only on distance from charge
Relation Between Electric Field and
Potential
• E = -dV/dr
• Electric field is negative gradient of potential
Graphical Representation
• V–r graph for point charge
• Slope gives electric field
Exam Tips
• Always state sign of charge
• Show full working
• Use correct units
Summary
• V = W/q
• V = kQ/r
• E = -dV/dr
Self Assessment
• A Van de Graaf generator has a charge
of 5.0×10−6 C. Calculate the electric potential
at a distance of 0.5m away from the centre of
the generator.