Question

What is the potential gradient between two parallel plane conductors when their separation is 20 mm and a p.d. of 400 V is applied to them?

Calculate the force on an oil drop between the plates if the drop carries a charge of 8 × 10^-19C.

Answer 1

a) We can find the potential gradient between two parallel plane conductors from the formula:

$$E=\dfrac{V}{d}=\dfrac{400\ V}{0.02\ m}=2.0\cdot10^4\ \dfrac{V}{m}.$$

b) We can find the force on an oil drop between the plates from the formula:

$$F=qE=8.0\cdot10^{-19}\ C\cdot2.0\cdot10^4\ \dfrac{V}{m}=1.6\cdot10^{-14}\ N.$$

Answer:

a) $E=2.0\cdot10^4\ \dfrac{V}{m}.$

b) $F=1.6\cdot10^{-14}\ N.$