# Homework Help: Potential and work done by the charge

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1. Mar 14, 2015

### xamy

1. The problem statement, all variables and given/known data

Tis is my attempt to the question so far. I am not sure about the answers if anyone please confirm them whether I have done the solution correctly or not especially for part 1.4 and 1.6.
Can anyone also guide me about how to do the last part.

1. A chargeQ =-10.0 nC is located 0.30 m from pointA and 0.50 m from pointB.
1.1. What is the potential at A?
1.2. What is the potential atB?
1.3. If a point chargeq is moved fromA toB whileQ is fixed in place, through what potential difference does it move?
1.4. Does its potential increase or decrease?
1.5. Ifq =-26.5 nC, what is the change in electric potential energy as it moves fromA toB?
1.6.Does the potential energy increase or decrease?
1.7. How much work is done by the electric field due to chargeQ as q moves fromA toB?

2. The attempt at a solution

1.1
VA=kq/r

=(9x109)(10n)/0.3

=300V

1.2
VB=kq/r

=(9x109)(10n)/0.5

=180V

1.3
ΔV=VA-VB

=300-180

=120V

1.4
Decrease

1.5
ΔUE=qΔV

=(26.5n)(120)

=3.18uJ

1.6
decrease

2. Mar 14, 2015

### ehild

You substituted wrong value for the charge - everywhere. The sign of the charge can not be ignored!

3. Mar 14, 2015

### xamy

Alright is answer to question 1.4 and 1.6 correct?? Secondly can you guide me how to solve qtn 1.7