Page 24 - Physics_Form_2
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Physics for Secondary Schools
Similarly, when a negatively charged
electroscope is earthed by a wire, Task 1.2
the excess electrons flow from the Use rubbing and direct contact
electroscope to the earth, causing the techniques to charge and discharge
electroscope leaf to collapse, causing it to an electroscope, then analyse and
discharge. share your findings with peers.
FOR ONLINE READING ONLY
Activity 1.9
Application of the electroscope
Aim: To investigate the charging
and discharging of a leaf Applications of an electroscope include:
electroscope by induction 1. Testing for the sign of charge on a
Materials: leaf electroscope, a piece body
of cotton cloth, a glass rod The leaf divergence increases when
a negatively charged ebonite rod is
Procedure brought near a negatively charged
1. Rub a glass rod with a piece of cotton leaf electroscope. Introducing a
cloth. material of unknown charge near the
2. Bring the rod near but not touching cap will cause the leaves to collapse
the brass cap of the electroscope. if it is positively charged. To test for
3. Record your observations. a negative charge, the electroscope
4. With the rod still near the cap, touch must first be positively charged;
the cap with an earthed wire. if the leaves collapse, the material
5. Note what happens. is negatively charged. However,
6. Remove the rod. a decrease in divergence can also
7. Now rub the glass rod with a piece occur with uncharged objects, so an
of wool, causing the rod to become increase in divergence is the sure
positively charged. test for charge presence.
8. Bring the positively charged glass
rod near but not touching the brass Table 1.2: Charges and their effects on the
cap of the electroscope. leaf electroscope
9. Remove the glass rod. Charge A charge Effects
on the is brought on leaf
electroscope near the cap divergence
Questions + + increase
(a) What happened to the electroscope? increase
Why? ˗ ˗
(b) Which type of charge is on the leaf + ˗ decrease
decrease
of the electroscope? + or - uncharged
body
18
Student’s Book Form Two
Physics Form 2 Final.indd 18 25/10/2025 10:25
