Gravitational and Electric Fields

• Gravitational fields affect all objects, while electric fields only affect objects with a charge
• Gravitational field strength (G) has the unit Newtons per kilogram and is 9.81 on Earth
• Gravitational field lines around Earth diverge, with closer lines indicating a stronger field
• Electric field lines show the direction of force on a positive charge, pointing away from positive charges
• Gravitational field strength is proportional to the mass creating the field and inversely proportional to the distance squared from its center
• Universal gravitational constant (Big G) is 6.67 * 10^-11
• Electric field strength (E) constant is 9 * 10^9, often represented as K
• Gravitational potential energy is -GMm/R and electric potential energy is KQq/R
• Potential energy is measured in Joules per kilogram or Joules per Coulomb
• Potential is zero at infinity for both gravitational and electric fields
• Field strength is the potential gradient, V/R
• Speed of a satellite is root GM/R and period of orbit is proportional to R^3
• Geosynchronous orbit satellites have a 24-hour period and stay above the same point on Earth's equator
• Escape velocity at the surface of a planet is root 2GM/R
• Distance of closest approach is the minimum distance a charged particle reaches before turning back
• For a uniform electric field, field lines are parallel and equipotentials are perpendicular to field lines
• Electric field strength is V/D for parallel plates
• Charged particle motion in an electric field is parabolic if entering at a right angle
• In levitation experiments, the force due to gravity equals the force due to the electric field