Calculate the work needed to move a test charge from point B to D

[shashaeee]

Calculate the work needed too move a 1.5μC test charge from point B to D.

Can someone just check if I'm thinking correctly?

Do I just use the formula:

W = qEd ?

For the E, I calculate the magnitude and direction of the electric field at B.
And I use 25cm for the distance and q = 1.5μC

 

[TSny]

W = qEd only works (pun?) if E is uniform. Instead, relate the work to electric potential or electric potential energy.

 

[shashaeee]

Ohhh, I see. So basically, the work needed to bring 1.5μC from a distance (25cm) away to a point 25cm from a charge 75μC?

Would it make sense to use this formula?


W = q(V_a - V_b)
W = q[(k*Q_a/r_a) - (k*Q_b/r_b)]

q = 1.5μC
Q_a = 75μC
Q_b = 1.5μC

r_a(75μC to D) = 25cm
r_b(B to D) = 25cm

 

[TSny]

That's more like it. But, since the charge is being carried from B to D, you'll need to find the potential difference in going from B to D. How would you find the potential at point B due to the two 75 μC charges? Point D?

 

[shashaeee]

ohhh, righttt.

So, rewriting it ..

W = q(V_D - V_B)

V_D = V_D1 + V_D2

V_B = V_B1 + V_B2

where the distance for V_D is 25cm
and the distance for V_B is 35cm

 

[TSny]

Yes, Good!

 

[shashaeee]

oh, thank goodness lol! Thank youu!