Charge, Potential, Work, and Electricity

[Phoenixtears]

SOLVED

Homework Statement

Moving a charge from point A, where the potential is 275 V, to point B, where the potential is 150 V, takes 4.0 10-4 J of work. What is the value of the charge?

Homework Equations

V= w/q

V= change in voltage
w= work
q= charge

The Attempt at a Solution

This problem seems simple enough, but for some reason I can't get the right answer. W= 4E-4 and then I divided it by the change in V (275- 150).

4E-4/ 115= 3.478E-6

Then I mulitplied by 1E6 to change the units into micro-Coulombs.

Yet this answer is wrong. What am I doing incorrectly??

Thanks in advance for the help!

~Phoenix

 

[lanedance]

first 150-275 = 125 not 115

i thin you may have to be careful with signs here as well

hint dV = V2-V1, if it takes work to move a charge to a smaller potential can we say something about the charge?

Think which way the electric field is pointing and how a positive charge would want to move between the points

 

[Phoenixtears]

Oh... I see what you're saying. (Sorry about the 115 thing, that was just my typing... the actual calculation was correct).

So instead it would be 4E-4/(150-275)= -3.2 Micro-C. Thanks so much! That makes perfect sense.