Page 25 - Physics_Form_2

Static electricity

2. Identifying the insulating at the specific point. Therefore, there
properties of materials is a difference in electrostatic potential
An electroscope that is positively between any two points in the electrostatic
charged can be used to test for the force field.
insulating properties of materials. If Potential of a charged body
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the material that is placed near the
cap of an electroscope is a conductor, A charged body is considered to be at a
positive potential if, upon grounding,
then the metal leaf collapses. If the electrons flow from the earth to the body.
material being tested is an insulator, Similarly, if electrons move from the
the leaf electroscope retains its body to the earth upon contact, the body
charge, and the leaf remains raised. is at a negative potential. This electron

flow continues until the body’s potential
3. Detecting the presence of charge matches that of the Earth, which is defined
on a body as zero potential as indicated in Figure

When a charge is induced on the 1.24. Therefore, any grounded conductor
leaf electroscope by a charged body, is considered to be at zero potential by
the leaf diverges. When the charged definition.
body is removed, the leaf collapses, Positive potential Negative potential
indicating that the induced charge
on the electroscope is temporary and
due to the charged body. Electron flow Electron flow
Earth's
surface
Electrostatic potential
You have learnt that like charges repel
each other, and unlike charges attract
each other. Therefore, work must be Figure 1.24: Flow of electrons to and from the
done to overcome the repulsive force in body and the Earth
moving a positive charge towards another
positive charge. Likewise, work is done Potential difference (p.d.) refers to the work
to overcome the attractive force to move required to move a charge between two
a negative charge away from a positive points with different electric potentials,
charge. The above processes apply to measured in volts (V). The volt is named
all points in the region surrounding any after the Italian physicist Alessandro Volta,
charges. This means an electrostatic force where one volt equals one joule of work per
field around a charge exists. The work coulomb of charge. In a leaf electroscope,
required to move a unit charge from a leaf divergence occurs due to this potential
reference point to a specific point against difference between the leaf and the cap.
the electrostatic force field of another When a negatively charged conductor is
charge is called the electrostatic potential grounded, negative charges flow from it

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Physics Form 2 Final.indd 19 25/10/2025 10:25