The electric field near the surface of Earth points downward and has a magnitude of 150 N/C.
(a) Compare the upward electric force on an electron with the downward gravitational force.
? (upward force / downward force)
The gravitational force is is much larger?
The electric force is is much larger?
Both forces are equal?
.

(b) What magnitude charge should be placed on a penny of mass 6 g so that the electric force balances the weight of the penny near Earth's surface?
? C

(a) Electric field is much larger

(b)

Explanation:

An electron being negatively charged will experience a force in a direction opposite to that of the electric field, that is, the force will be upwards (electric field being downwards).

The force experienced by the electron due to the electric filed is given by:

Force due to gravity (downward direction):

Hence, the electric field is much larger.

It is given that a penny has mass

Gravitational force = mg = 0.05886 N

To balance that we have to put, say, q amount of negative charge on the penny. Therefore,

or,

c) up is the direction the magnetic force is acting on the charge.