ELECTROSTATICS

SS 1 PHYSICS FIRST TERM E-LEARNING NOTE

Subject: 

PHYSICS

Term:

FIRST TERM

Week:

WEEK 6

Class:

SS 1

Topic:

ELECTROSTATICS

Previous lesson: 

The pupils have previous knowledge of

HEAT ENERGY TRANSFER OF HEAT

that was taught as a topic in the previous lesson

 

Behavioural objectives:

At the end of the lesson, the learners will be able to explain each of the following concepts and relate how they are used or related.

1. Definition of Electrostatics
2. Types of Charges
3. The Law of Electrostatics
4. Gold leaf Electroscope
5. Ways of Producing Charges
6. Charge Distribution in a Conductor
7. Lightning Conductors
8. Electrophorus

Instructional Materials:

• Wall charts
• Pictures
• Related Online Video
• Flash Cards

 

 

Methods of Teaching:

• Class Discussion
• Group Discussion
• Asking Questions
• Explanation
• Role Modelling
• Role Delegation

 

Reference Materials:

• Scheme of Work
• Online Information
• Textbooks
• Basic Education Curriculum
• Workbooks

 

CONTENT:

ELECTROSTATICS

CONTENT

1. Definition of Electrostatics
2. Types of Charges
3. The Law of Electrostatics
4. Gold leaf Electroscope
5. Ways of Producing Charges
6. Charge Distribution in a Conductor
7. Lightning Conductors
8. Electrophorus

 

Definition of Electrostatics

Electrostatics is the study of charges at rest. It is electricity that does not move from one point to another in the substance in which it is produced.

 

Types of Charges

Positive charge

A body becomes positively charged if it losses electron. This can be obtained in the Laboratory if glass rod is rubbed with silk and there is a net transfer of surface electrons from glass to the silk. The glass becomes positively charged and the silk becomes negatively charged.

Negative charge

A body is negatively charged if it gains electron. This is obtained by rubbing ebonite rod with fur and there is a transfer of electrons from the atoms of fur to the ebonite rod. The fur becomes positively charged.

The positively charged protons deep in the nucleus are not free to be transferred. Hence bodies do not become electrically charged by transfer of protons. They become charged by transfer of electrons

The Law of Electrostatics

Like or similar charges repel each other; unlike or opposite charges attract each other.

 

Gold leaf Electroscope

An electroscope is an instrument used for the detection and testing of small electric charges. It consists of a flat brass disc or cap, a brass rod with a gold leaf. The metal case is made draught-proof and connected to the earth to prevent accumulation of charges due to external influence.

Uses of the Gold Leaf Electroscope

1. To detect charges: If a charged body is placed on the cap of a charged  electroscope an increase in divergence or collapse of the leaf shows the body is charged. If there is no change in the divergence, it means the body is not charged.
2. To determine the nature of charge on the body: If a charged body is placed on a charged electroscope, increase in divergence means the charge on the electroscope and the body are the same. If there is collapse of the leaf, it means they have opposite charge or the body is uncharged.
3. To determine the conducting properties of a body: If a good conductor is placed on the cap of an electroscope, the leaf collapses immediately. If it is a semi conductor, it collapses gradually and if an insulator, there is no alteration of the leaf

EVALUATION

1. What is electrostatics?
2. Explain three functions of a Gold leaf electroscope

 

Ways of Producing Charges

1. Electrostatic Induction: 

Electrostatic induction is the act of charging a neutral body by placing a charged body near it without any contact between the two.

STEP 1: A negatively charged body is brought near the uncharged body, free electrons from the metal sphere are repelled by the excess electrons on the rod. They shift towards the right. They can not escape from the sphere because the stand and the surrounding air are insulated.

STEP 2: These excess charges called induced charges are released to the earth by touching the right part of the sphere with a wire and the other part of the wire to the earth.

STEP 3: The wire is disconnected.

STEP 4: The negatively charged rod is removed. A net positive charge is left on the rod.

2. Friction:

Charges can also be produced by friction. By rubbing as in ebonite and fur, glass rod and silk, charges are transferred from one by either of the two bodies involved. Equal and opposite charges are produced by friction.

Effects of Charging by Friction

1. Passengers stepping out of cars and buses complain of a slight electric shock as soon as their feet touch the ground.This is because friction between the air and the body of the fast moving car makes the body of the vehicle to be charged.
2. A chain is often left hanging from the rear of a petrol tanker to discharge the charges acquired on the body during movement as this may cause a spark when inflammable vapour is present.
3. Contact: This is done by bringing a charged body in contact with an uncharged body. Charges are transferred from the charged body to the uncharged body.

 

Charge Distribution in a Conductor

Charges are usually concentrated at places where the surface is sharply curved. The charge density is highest at the sharpest point of the conductor. Because of this high charge density, air molecule close to this point get ionized ( i.e broken down into positive and negative ions). Those with charge opposite to the conductor will be attracted to the conductor. Those with charge opposite to that of the conductor will be repelled. As these ions move, they collide with other molecules and knock off electron from them thereby ionizing those molecules. This process could continue leading to a geometrical increase in the number of ions around the conductor.

For a hollow conductor, charges reside only on its outside surface, no charges reside inside the conductor.

EVALUATION

1. What is electrostatic induction?
2. Explain the three methods of charging.

 

Lightning Conductors

Lightning conductors are used to prevent tall buildings from being damaged when being struck by lightning. They are made from a copper with a sharp point edge or spike at the top. It helps to conduct the charges generated harmlessly to the earth. When electrical charges in thunderclouds build up, attraction between unlike charges within a cloud increases steadily until a heavy spark  and sound is produced as the charges approach one another. This spark is observed as lightning and the sound is thunder. The heat generated can set a building or tree on fire.

The charge on the cloud induces electrical charges on the lightening conductor. This buildup at the sharp edge and cause ionization of air molecule around it. Some of the charge avalanche result from the  ionization of air around the lightening conductor travels toward the cloud and help to neutralize some of the charge on the cloud thereby reducing the possibility of a lightening.

 

Electrophorus

Electrophorus is used for storing and transferring electric charges. It consists of a metal disc fitted with an insulating handle and another flat disc made of insulating material such as ebonite

 

GENERAL EVALUATION

1. Explain the use of the following: (i) Lightning conductor (ii) Electrophorus

 

ELECTROSTATICS

CONTENT

1. Definition of Electrostatics
2. Types of Charges
3. The Law of Electrostatics
4. Gold leaf Electroscope
5. Ways of Producing Charges
6. Charge Distribution in a Conductor
7. Lightning Conductors
8. Electrophorus

 

Determining the amount of charge on an object

Applications of Electrostatics

Electrostatics is the study of electric charges at rest. In everyday life, static electricity is often created by rubbing certain materials together, like when you rub a balloon on your head to make your hair stand up

There are two types of electric charges, positive and negative. Like charges repel each other, while opposite charges attract each other. The Law of Electrostatics states that the force between two objects is proportional to the product of their electric charges and inversely proportional to the square of the distance between them.

The amount of charge on an object can be measured using a device called a Gold leaf Electroscope. This device consists of two metal leaves that are connected to each other by a metal rod. When an object with a charge is brought near the leaves, the leaves will either be attracted to or repelled from each other, depending on the type of charge on the object.

Charges can be produced in a number of ways, including rubbing two objects together, using a battery, or by exposing an object to radiation. Conductor is a material that easily allows charges to flow through it, while an insulator is a material that does not allow charges to move easily.

When a conductor is charged, the charges will distribute themselves evenly throughout the conductor. However, if an insulator is charged, the charges will stay concentrated on the surface of the material. This is why it is important to use insulation when working with electrical wires.

Lightning is a natural phenomenon that occurs when there is a build-up of static electricity in the atmosphere. Lightning rods are used to protect buildings from lightning strikes by providing a path for the electricity to travel through.

The Electrophorus is a device that can be used to create static electricity. It consists of a metal plate and a non-conductive rod. The plate is charged by rubbing it with a material that has a charge, such as a balloon. The rod is then placed on the plate and the charge will be transferred to the rod. The Electrophorus can be used to create a high voltage, which is useful for applications such as electrostatic painting.

When an object has a net charge, it means that the number of protons is not equal to the number of electrons. The protons are positively charged, while the electrons are negatively charged. The net charge of an object can be calculated by subtracting the number of protons from the number of electrons.

Electrostatics is a branch of physics that deals with the study of electric charges at rest. It is a fundamental area of physics that explores the relationships between electricity and matter.

Write out ten questions about the topic and answer them.

1. What is the definition of electrostatics?

2. What are the two types of electric charges?

3. What is the Law of Electrostatics?

4. What is a Gold leaf Electroscope?

5. How can charges be produced?

6. What is a conductor?

7. What is an insulator?

8. What is lightning?

9. What is the Electrophorus?

10. What is the net charge of an object?

1. Electrostatics is the study of electric charges at rest.

2. There are two types of electric charges- positive and negative.

3. The Law of Electrostatics states that the force between two objects is proportional to the product of their electric charges and inversely proportional to the square of the distance between them.

4. A Gold leaf Electroscope is a device used to measure the amount of charge on an object.

5. Charges can be produced by rubbing two objects together, using a battery, or by exposing an object to radiation.

6. A conductor is a material that easily allows charges to flow through it.

7. An insulator is a material that does not allow charges to move easily.

8. Lightning is a natural phenomenon that occurs when there is a build-up of static electricity in the atmosphere.

9. The Electrophorus is a device used to create static electricity.

10. When an object has a net charge, it means that the number of protons is not equal to the number of electrons. The net charge of an object can be calculated by subtracting the number of protons from the number of electrons.

 

1. What is the definition of electrostatics?

A) The study of electric charges in motion

B) The study of electric charges at rest

C) The study of magnetic fields

D) The study of nuclear physics

2. What are the two types of electric charges?

A) Positive and negative

B) Up and down

C) Left and right

D) North and south

3. What is the Law of Electrostatics?

A) The force between two objects is proportional to the product of their electric charges and inversely proportional to the square of the distance between them.

B) The force between two objects is inversely proportional to the product of their electric charges and proportional to the square of the distance between them.

C) The force between two objects is inversely proportional to the square of the distance between them.

D) The force between two objects is proportional to the square of the distance between them.

4. What is a Gold leaf Electroscope?

A) A device used to measure the amount of charge on an object.

B) A device used to measure the electric field strength.

C) A device used to measure the current in a circuit.

D) A device used to measure the resistance of a material.

5. How can charges be produced?

A) By rubbing two objects together

B) By using a battery

C) By exposing an object to radiation

D) All of the above

6. What is a conductor?

A) A material that easily allows charges to flow through it.

B) A material that does not allow charges to move easily.

C) A material with a high melting point.

D) A material that is not affected by magnetic fields.

7. What is an insulator?

A) A material that does not allow charges to move easily.

B) A material that easily allows charges to flow through it.

C) A material with a low melting point.

D) A material that is affected by magnetic fields.

8. What is lightning?

A) A natural phenomenon that occurs when there is a build-up of static electricity in the atmosphere.

B) A natural phenomenon that occurs when there is a build-up of kinetic energy in the atmosphere.

C) A natural phenomenon that occurs when there is a build-up of potential energy in the atmosphere.

D) A man-made phenomenon that occurs when there is a discharge of static electricity.

9. What is the Electrophorus?

A) A device used to create static electricity.

B) A device used to measure static electricity.

C) A device used to store static electricity.

D) A device used to conduct electricity.

10. What does it mean when an object has a net charge?

A) The number of protons is equal to the number of electrons.

B) The number of protons is greater than the number of electrons.

C) The number of protons is less than the number of electrons.

D) The object has no charge.