Question

1. Two charges Q1 = +5 nC and Q2 = -7 nC are being separated

by 8 cm. Calculate the electric potential at point A. Refer to

the figure on the left.

2. A research Van de Graaff generator has a 2.50 mm diameter

sphere with a charge of 6.00 μC on it.

A. What is the potential near its surface?

B. At what distance from its center is the potential 1.50 MV?

Please put what letter you answered

Answer 1

A. What is the potential near its surface?

$$V=k\frac{q}{r}\\ =9*10^9*\frac{6*10^{-6}}{1.25*10^{-3}}=4.3*10^7\:\rm V$$

B. At what distance from its center is the potential 1.50 MV?

$$r=\frac{kq}{V}\\ =\frac{9*10^9*6*10^{-6}}{1.5*10^6}=0.036\:\rm m=36\: mm$$