Under the influence of the Coulomb field of charge `+Q`, a charge `-q` is moving around it in an elliptical orbit. Find out the correct statement(s).

Options

A. The angular momentum of the charge - q is constant
B. The linear momentum of the charge-q is constant
C. The angular velocity of the charge-q is constant
D. The linear speed of the charge-q is constant

Answer

A

Explanation

This is similar to motion of planets around sun in elliptical orbits. In this case torque of Coulomb force (Q) on the charge -q is zero as `(dL)/(dt)=0 " " therefore ` L = constant
Hence the angular momentum of -q is constant.
`therefore` (a) is the correct option.
All other options are wrong because in the elliptical orbit, v is not constant and hence linear momentum and angular velocity will not remain constant.