© Department of Physics, University of Guelph.

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1. Potential differences between some pairs of
points are given below. Calculate the unknown potential differences
V_{CA}, V_{AD}, V_{DB}.

Hint: When considering potential differences one may arbitrarily assign
any point a potential of zero (rather than "zero at infinity"). E.g., if
you set V_{A} = 0, then V_{B} must be +5 V (since
V_{BA} = 5 V); continue for values of V at C and D and then
determine V_{CA} etc.

2. At a point A near some ions in solution, the potential is 50 V, i.e.,
V_{A} = 50 V relative to 0 at infinity.

(a) What "electrical work" (i.e., work against
the E-field of the ions must you do to move a
SO^{=}_{4}
at constant speed (no KE change) from infinity to point A?

(b) What "electrical work" would you have to do
to move the SO^{=}_{4} back from A to infinity?

(c) What is the electrical PE of the
SO^{=}_{4} ion at the point A?

(d) What work would the electric field do on the
SO^{=}_{4} ion if it moves from A to infinity?

3. Referring to Question 2. At a second point B, the potential is
V_{B} = -20 V.

(a) What electrical work must you do to move the
ion at constant speed from A to B?

(b) What is the change in the
SO^{=}_{4} ion's electrical PE when it goes from A to B?