- #1
Reneee
- 4
- 2
- Homework Statement
- A charge Q in point O=(0,0) and a test charge q in point A=(4,1) lie in a plane.
How much work W needs to be done to move q to point B=(2,2).
Q always stays at (0,0).
Q=q= 2*10^-4. One unit here equals 1 meter.
- Relevant Equations
- no equations.
I found two formulas to calculate the work done. One is with this path integral:
## W_{AB}## = W(## r_A,r_B ##)=q* ## \int_{r_A}^{r_B} E*dr ##
but here is the one I tried to use:
## W_{AB}## = q*Δ U = q*(## \frac {kQ} {r_A} ## - ## \frac {kQ} {r_B} ## )
Now here's my problem, what are the distances## r_A ##and ##r_B ## that i have to plug in?
Can I just use: the length ##r_A ##=## | \vec {OA} |## = ## \sqrt 17## ## r_B ## = ##| \vec {OB} | ## = ##\sqrt 8 ##.
Or do I have to do something else, like do I maybe need to follow the equipotential lines(please say no x) ) like this?:
If so ,then how can I put this into mathematics, especially the path ##\vec {BC}##, so I can use it in one of the equations?
~note: for all intents and purposes I didn't knew anything about physics until last week ,when we covered physics for 2 lessons in my cs-course, please excuse me if i am missing some of the very basics.