Page 11 - Physics_Form_2

Static electricity

Example 1.1 (ii)
A charged sphere is brought into contact Step 1: Identify the initial location
with an object of unknown material. The where the charges are added
sphere transfers electrons to the object, to the object and their final
and the charge distribution is measured locations after a brief period of
after a short period of time. time. A group of electrons has
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been removed from a specific
location on the object. After
short period, this region of net
positive charge (due to electron
(a) deficity) remains fixed in the
same location.
Step 2: If the charges are spread evenly
across the surface of the object,
(b) it is a conductor. If the charges
remain in the same location
Figure 1.5
where they were added, it is an
Based on the charge distribution: insulator. Based on the charge
(i) is the object in Figure 1.5 (a) a distribution, the object is an
conductor or an insulator? insulator.
(ii) is the object in Figure 1.5 (b) a
conductor or an insulator? Air as a conductor: Air is an insulator.
However, under certain conditions,
Solution sparks or lightning occur, allowing
(i) charge to move through the air as if it
Step 1: Identify the initial location where were a conductor. The sparks that jump
the charges are added to the between your fingers and a doorknob after
object and their final locations you have rubbed your feet on the carpet
after a brief period of time. The discharge you. That is, you have become
electrons are initially located in neutral because the excess charges have
a group where they were added left you. Similarly, lightning discharges
and are then spread out evenly from a thundercloud. In both cases, for a
across the surface of the object. brief moment, air becomes a conductor.
Step 2: If the charges are spread evenly Separation of charge
across the surface of the object, If two neutral objects are rubbed together,
it is a conductor. If the charges each can become charged. For instance,
remain in the same location when rubber and wool are rubbed
where they were added, it is together, electrons from the atoms of
an insulator. Therefore, because the wool are transferred to the rubber,
the charges are distributed as shown in Figure 1.6 (a) and (b). The
evenly, the object is a conductor. extra electrons on the rubber result in a

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Physics Form 2 Final.indd 5 25/10/2025 10:25