(ii) the capacitance of the capacitor if the dielectric is changed from air to mica, distance between plates remains 2 mm, with full area of overlap
(iii) the capacitance of the capacitor if distance between plates is reduced to 1 mm,
SAMPLE ANSWER 16C Using the formula
C Ae d
(i)
CeA d
(0.01)(8.9 1012) 0.002
the dielectric is air, with full area of overlap
(iv) the capacitance of the capacitor if the area of overlap is halved, the dielectric is air, distance between plates remains 2 mm.
, making sure all values are in their standard unit: l 10 cm 0.1 m, d 2 mm 0.002 m; A (01)2 0.01 4.45 1011 F Dielectric = air (iii)
CeA d
(0.01)(8.9 1012) 0.001
8.9 1011 F Dielectric = air
d = 2 mm Fig 16.7 (ii)
C eA d
(0.01)(6.2 1011) 0.002
3.1 1010 F (iv)
CeA d
Dielectric = mica Dielectric = air d = 2 mm d = 2 mm Fig 16.8 Charging a capacitor (storing energy)
Consider the circuit diagrams in Figs 16.11(a) and (b). Electrons flow from the negative terminal of the battery to the right-hand plate of the capacitor.’
Electrons flow from the negative terminal of the battery to the right-hand plate of the capacitor.
Electrons also flow from the left-hand plate of the capacitor to the positive terminal of the battery.Thus negative charge builds up on the right-hand plate of the capacitor and positive charge builds up on the left.
