Electric Fields

A field line is normal to an equipotential surface

• for both electric and gravitational fields

• for electric but not gravitational fields

• for gravitational but not electric fields

• for neither electric nor gravitational fields

The mass of a planet is M and its radius is R. In order for a body of mass m to escape the gravitational attraction of the planet, its kinetic energy at the surface of the planet must be at least

• $\frac{GMm}{R}$

• $\frac{GMm}{R^2}$

• $\frac{GM}{R}$

• $\frac{GM}{R^2}$

The diagram shows two point charges P and Q. At which position is the electric field strength equal to zero?

• Option A

• Option B

• Option C

• Option D

At the surface of a planet of radius r, the gravitational field strength is g and the gravitational potential is V. Which gives the gravitational field strength and gravitational potential at a height 3r above the surface?

• Option A

• Option B

• Option C

• Option D