What electric potential would be measured at a distance of 12cm from a charge of 3.5 x 10-5 c? what would be the potential if the distance were increased to 30 cm?
how much work must be done to carry a 3.0 x 10-5 c charge from 12 cm to 30 cm?

1.

The electric potential produced by a single point charge is

where

k is the Coulomb's constant

q is the charge

r is the distance from the charge

In this problem,

so the electric potential is

2.  

Applying the same formula used before

The electric potential produced by a single point charge is

where in this case we have

the electric potential is

3. 644 J

The work done to carry a charge q through a potential difference of is given by

In this problem, we have

is the charge

is the potential difference

Therefore, the work done is

it has to be b, about 97 percent.

what is the actual question though?