# Physics help! -What is the electric potential at a point midway between the charges?

Two point charges Q1 = +4.50 nC and Q2 = -3.00 nC are separated by 37.0 cm.

(a) What is the electric potential at a point midway between the charges?

_______ V

(b) What is the potential energy of the pair of charges?

_______ J

1.) Negative work must be done to separate the charges.

or

2.) Positive work must be done to separate the charges.

(a) Electric potential= (1/4pi-epsilon nought)*(Q1/r1 + Q2/r2)

Midway so I assumed that the distance is .185 meters

Then, 9X10^9 Nm^2/C^2 (4.5X10^-9 C /0.185m + (-3.0X10^-9C/0.185m))

9X10^9 Nm^2/C^2 (1.5X10^-9/.185m)

answer: 72.97 V or 73 Volts

Potential Energy: -3.28X10^-25 J, formula is k=9X10^9 times (Q1Q2 all over distance(.37m))

if potential energy is negative like the one i got, it means that negative work must be done to assemble the charges and positive work must be done to separate them. if in case you got a positive potential energy it means that positive work must be done to assemble the charges and negative work must be done to separate them :) Hope i did it right, this is our lesson this past few days, and i'm also having a hard time understanding it ;)

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