Question

Can you please explain how these answers are correct?
An electric field measured near a point charge of 3.00 x 10-6 C has a strength of 1.5 x 105 N/C. How far is the point from the source charge?
0.42 m

Answer 1

For the electric field shown with a positive source charge, which of the following statements describes a decrease in voltage?

c. A positive charge moves across an equipotential line away from the source charge.

Answer 2

Coulumbs Law for first:

\[F = \frac{k \ q_1 \ q_2}{r^2}\]
gives equation for field strength nears a charge Q\[E = \frac{k \ Q}{r2}\]

k = 9 x 10^9

use equation for E....obviously.

for the second, you would expect same charged particles to repel each other. do you understand what is meant by equipotential and why motion would be perpendicular to these lines? potential is measured in volts, it is energy per unit charge.