A total charge Q is uniformly distributed through-out a spherical volume of radius a. Which of the following is a dimensionally correct expression for the potential difference between the center of the sphere and its surface? a. (1/8πε0)Q
b. (1/8πε0)Qa^2
c. (1/8πε0)Qa
d. (1/8πε0)Q/a
e. (1/8πε0) Q/a^2

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.