Question

Two 3.0 cm X 3.0 cm metal electrodes are spaced 1.0 mm apart and connected by wires to the terminals of a 9.0 V battery.

(a)What is the charge on each electrode? (pC)
(b)What is the potential difference between electrodes? (V)
(c)While the plates are still connected to the battery, inselated handles are used to pull them apart to a new spaceing of 2.0mm. What are the charge on each electrode? (pC)
(d) While the plates are still connected to the battery, inselated handles are used to pull them apart to a new spaceing of 2.0mm. What is the potential difference between electrodes? (V)

Answer 1

a)

we need to find capacitance

C = $\epsilon$ _oA / d

C = 8.85e-12 * 0.03 * 0.03 / 1e-3

C = 7.965e-12 F

so,

Q = CV

Q = 71.685 pC

-------------------------------------------------------

b)

V = 9 Volts

--------------------------------

c)

C = 8.85e-12 * 0.03 * 0.03 / 2e-3

C = 1.3275 pF

so,

Q =CV

Q = 11.95 pC

-------------------------------

d)

V = 9 V ( same, it is still connected)