Static Electricity 1

PHYSICS

UNIT 2 SHEET 1

PreIGCSE

Unit 2 Static Electricity

Exercise 1-1: Read the passage and then answer the following questions ➢ Everything is made of atoms. Under normal circumstances every atom in an object have equal number of electrons and protons ➢

However, sometimes when objects are rubbed together a few electrons jump from one object to the other. This leaves one object with too few electrons and another object with too many electrons. Polythene and Perspex are both types of plastic. All plastics are electrical insulators.

➢

Any object that is made from plastic can be electrically charged by rubbing it with a woolen cloth. If plastic is polythene, electrons will jump from the cloth to the polythene as they rub together. If the plastic is perspex, electrons will jump from the perspex to the cloth as they rub together

Polythene rod

Perspex rod

cloth cloth 1| Page

PHYSICS

UNIT 2 SHEET 1

(i)

PreIGCSE

When Perspex rod is rubbed with a woolen cloth, which becomes negatively charged and which becomes positively charged ? ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

(ii)

When a rod of polythene is rubbed with a woolen cloth which becomes negatively charged and which becomes positively charged ? ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Having charged the Perspex and polythene rods, the following experiment is carried out. The charged Perspex rod is hung by a thin string so that it is free to move around as shown in diagram 1. The charged polythene rod is held close to the Perspex rods Polythene

Perspex

A Perspex Diagram 1 2 2| Page

Diagram

PHYSICS

UNIT 2 SHEET 1

PreIGCSE

(iii) Describe what you see when this is done. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------(iv) In diagram 2, a charged Perspex rod is held close to a charged rod A. Rod moves away from the Perspex rod. What is the charge on rod A ? ------------------------------------------------------------------------------------------------

(v)

When long dry hair is brushed the strands move away from one another. Explain why this happens --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

(vi) As you brush strands of hair are also attracted to the bristles of the brush. Explain this. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------(vii) What are the types of electrical charges ? ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------(viii) Does the charge gained by the plastic rod depend on the type of plastic ? Give an example 3| Page

PHYSICS

UNIT 2 SHEET 1

PreIGCSE

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(ix) Will materials with like electrical charges attract or repel ? ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Exercise 1-2: When a balloon is rubbed on clothing, such as a woolen sleeve it gains electrons from the wool so it gains an electric charge Look at the following diagram then answer the following

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PHYSICS

UNIT 2 SHEET 1

PreIGCSE

Diagram 3 (i)

When the charged balloon is approached to a wall it gets stuck to it. Explain why this happens ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

(ii)

When 2 balloons are charged in the same way, and are suspended with nylon threads like in figure 3, they move away from each other. Why does this happen? --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

in which electrons can move freely from atom to atom so electric charge can flow readily n which electrons are firmly held in their atoms and cannot move so electric charges cann onductor of electricity

Gold-leaf electroscope 5| Page

PHYSICS

UNIT 2 SHEET 1

PreIGCSE

➢ The gold-leaf electroscope is composed of a metal stem or rod held inside a glass case by a block of insulating material. A metal cap (disc) is connected to the top of the stem and a metal plate at the bottom, with a thin leaf of gold foil attached. ➢ This apparatus is used to detect static electric charges and its types

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PHYSICS

UNIT 2 SHEET 1

PreIGCSE

➢ A gold-leaf electroscope can be used in 1- Detect a charge 2- Charging by contact 3- Detection of insulators and conductors

Exercise 1-3: 1-

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A student is using the gold-leaf electroscope in the detection of a charge he approaches a polythene negatively charged rod to the metal cap but he didn’t touch the cap with the rod and the gold-leaf rises as shown in the following figure, answer the following

PHYSICS

UNIT 2 SHEET 1

PreIGCSE

Explain why the gold-leaf rises away from the metal plate ? -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------(i)

(ii)On the previous diagram illustrate the formed charges on the metal cap and the gold-leaf

1- A student draws a charged polythene rod firmly across the edge of the metal cap as shown in the following diagram. Answer the following

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PHYSICS

UNIT 2 SHEET 1

PreIGCSE

(i) What is the name of the method the student used in charging the metal plate ? -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------(ii)Draw a diagram of the electroscope showing the charges on the cap and gold-leaf after the student removes the rod

(iii)What will happen if the student touches the charged metal cap ? What is that called ? 9| Page

PHYSICS

UNIT 2 SHEET 1

PreIGCSE

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------(iv)Explain how would you use the gold-leaf electroscope in detection of insulators and conductors --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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