Page 27 - Physics_Form_2

Static electricity

charged negatively, and the other plate positively. The charge continues to accumulate
on the plates with time until the capacitor is fully charged. Figure 1.26 (a) shows a
capacitor, (b) its structure and (c) its circuit symbol.
Conductive
parallel plates
Q+ Q-
FOR ONLINE READING ONLY
+ -
+ -
+ -
+ -
+ -
+ -
Symbol
Dielectric
Capacitor + - (c)
(a) Voltage

(b)

Figure 1.26: Capacitor and its symbol

Capacitors are used as parts of electrical circuits in A fully charged capacitor
many common electrical devices. They store energy has a positive charge on one
in the electrostatic field created by the electric plate and an equal amount of
charges on their plates. Consider electric devices negative charge on the other.
like the radio or stereo system; the power lamp fades The potential difference
out slowly when power is switched off. On the other between the capacitor plates
hand, the stereo system has its sound playing for is measured by connecting a
some seconds after the power is switched off. This is voltmeter across them.
because capacitors store electrical energy, and, as a
result, the electronic appliances then continue being Capacitance
supplied with it. Capacitors are used in computers, When more charges are
televisions and other electronic circuits. Figure 1.27 added to the capacitor, the
shows mounted capacitors in a radio circuit board. value of its positive and

negative potential rises. Why
Capacitor
does this happen? The reason
is that the increased charge
repels any incoming charge
more strongly than before.
Thus, more work has to be
done to increase the charge
on the capacitor. A measure
of the amount of charge the
Figure 1.27: Capacitors in a radio circuit board capacitor (or any conductor)

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Physics Form 2 Final.indd 21 25/10/2025 10:25