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Capacitor Questions

Q1. The graph shows how the charge of a capacitor varies with the p.d. across it.

Use the graph to find - Note you are asked to 'use the graph' - so show how you do that!

a) the energy stored by the capacitor when charged to a potential difference of 8 V

Area under graph (equiv to ½ QV) = energy

Mark for marking the line on the graph to outline the area to be calculated

E = ½ x 3.5 x 10-3 x 8

E = 0.014 J

(3 marks)

b) the capacitance of the capacitor

Gradient of the graph = Q/V = C

Mark for using a 'large' triange - smallest side 8 cm

gradient = Δy/Δx

C = (3.5 x 10-3 - 0.0)/ (8.0 - 0.0)

C = 4.4 x 10-4 F

 

(3 marks)

(Total 6 marks)