Gravitational Equipotential Surfaces (HL) (HL IB Physics)

• Equipotential lines (when working in 2D) and surfaces (when working in 3D) join together points that have the same gravitational potential
• These are always:
• Perpendicular to the gravitational field lines in both radial and uniform fields
• Represented by dotted lines (unlike field lines, which are solid lines with arrows)

• In a radial field (eg. a planet), the equipotential lines:
• Are concentric circles around the planet
• Become further apart further away from the planet

• In a uniform field (eg. near the Earth's surface), the equipotential lines are:
• Horizontal straight lines
• Parallel
• Equally spaced

• Potential gradient is defined by the equipotential lines

• No work is done when moving along an equipotential line or surface, only between equipotential lines or surfaces
  • This means that an object travelling along an equipotential doesn't lose or gain energy and ΔV =  0

Gravitational equipotential lines in a non-uniform and uniform gravitational field

• The distinction between radial and uniform fields is an important one

• In a radial field (eg. a point charge), the equipotential lines:
• Are concentric circles around the charge
• Become further apart further away from the charge
• Remember: radial field is made up of lines which follow the radius of a circle

• In a uniform field (eg. between charged parallel plates), the equipotential lines are:
• Horizontal straight lines
• Parallel
• Equally spaced
• Remember: uniform field is made up of lines which are a uniform distance apart