Page 19 - Physics_Form_2

Static electricity

Detection of charges
Electroscopes detect the presence of
electric charges on a body. The most
commonly used type of this instrument is
the leaf electroscope.
FOR ONLINE READING ONLY
Structure of a leaf electroscope
Conduction
electrons A leaf electroscope was previously
attracted referred to as a gold leaf electroscope.
It is an instrument used to detect electric
charge on an object. It consists of a metal
cap mounted on a metal rod, having at
its lower end a small metal plate with a
thin metal leaf attached to it. The metal
used for the cap, rod and plate is normally
Figure 1.16: Charging a conductor brass. The leaf is normally made up of
by induction using a gold, but any other metal, like aluminium,
positively charged rod can be used. The metal rod and plate
with attached metal leaf are enclosed in
If the charging object (comb or glass rod) a metal or glass case to protect the leaf
is removed, the charges in the iron nail from air currents. Figure 1.17 (a) shows
return to their normal distribution and the an example of a leaf electroscope, and
nail is no longer charged. Figure 1.17 (b) is its schematic diagram.

Brass cap Brass cap

Insulator Insulator
Glass window
Brass rod Brass rod
Brass plate Earthed
Leaf metal
Earthed Metal leaf case
metal case
Brass plate

(a) (b)

Figure 1.17: Leaf electroscope

Construction of a gold-leaf electroscope

The construction includes a metal rod with a conductive ball at the top and two thin
gold leaves suspended from the bottom, which visibly respond to changes in charge.
Enclosed in a protective casing, the electroscope is an essential tool in electrostatics,
enabling clear observation of electrostatic phenomena.

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Physics Form 2 Final.indd 13 25/10/2025 10:25