• Learning Objectives
• Identify electrostatic force between charges
• Compare electrostatic force with gravitational force
• Describe the processes of charging an object by friction, conduction, and induction

Keywords

• Induction
• Conduction
• Friction
• Grounding

Electrostatic force

• Understanding electrostatic force using simulation

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• https://phet.colorado.edu/en/simulations/coulombs-law

Electrostatic force

• Instructions Activity 1
• Keep both a charge of 10 micro coulomb to both spheres and change the distance between them
• Observe , what happens to the force when the distance between them increases

Electrostatic force

• Instructions Activity 1
• Keep both spheres 5cm apart
• Increase charges on the sphere
• Observe what happens to the forces acting on them

Conclusion

The factors on which the force of attraction or repulsion between the charges depend

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1.

2.

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• Calculate the force between two charges

Electrostatic force

K =

• Electrostatic forces are typically stronger than gravitational force.
• Can be either positive or negative.
• There are two kinds of electric charge.
• Like charges repel and unlike charges attract.
• Charges exert forces on other charges at a distance.
• The force is stronger when the charges are together.

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SLO:Identify the characteristics of electric charge.

Electrostatic force

How can we detect charges on an object?

What is the name of the instrument ?

Electroscope

• An electroscope consists of a metal knob connected by a metal stem to two thin, lightweight pieces of metal foil, called leaves, that are enclosed to eliminate air currents. Used to detect electric charge.
• Figure shows a neutral, uncharged electroscope.
• Note that the leaves hang loosely.

SLO:Define an electroscope.

Electroscope

If you know the charge of electroscope

We can find the charge of unknown material

If the unknown charge on the material and the charge on the electroscope are same then the leaves of the electroscope will diverge ( move away)

SLO:Define an electroscope.

Conduction in an electroscope

SLO: Describe conduction in an electroscope

• Learning Objectives
• Identify electrostatic force between charges
• Compare electrostatic force with gravitational force
• Describe the processes of charging an object by friction, conduction, and induction

Keywords

• Induction
• Conduction
• Friction
• Grounding

Electrostatic force

Electrostatic force

How can we charge a material ?

Hint: There are three main methods of charging an object . Use the diagrams and find the names of these methods

Use chat box for answering

2.Method of charging: Conduction

• Charging a neutral object by touching that object with a charged object charging by conduction.
• One object should be neutral and the other must be charged.
• At the end of conduction both objects will have the same charge.

SLO:Describe conduction

Conduction: by bringing a negatively charged object

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• One object is neutral and the other is negatively charged.
• At the end of conduction both objects will have the same charge.

Conduction: by bringing a positively charged object

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• One object is neutral and the other is positively charged.
• At the end of conduction both objects will have the same charge.

Charging by conduction

• Charging by conduction When you touch a negatively charged rod to the knob of an electroscope, electrons are transferred to the knob and spread over all the metal surfaces.
• The two leaves become negatively charged and repel each other, so they move apart.

SLO: Describe conduction in an electroscope

Charging by conduction

• Charging by conduction When you touch a positively charged rod to the knob of an electroscope, electrons are transferred from the leaves to the rod.
• The two leaves become positively charged and repel each other, so they move apart.

SLO: Describe conduction in an electroscope

Charging by induction

• The process of charging a neutral object by bringing a charged object near it is called charging by induction the diagram below shows charging by induction try to find the reason behind this charging

SLO: Describe conduction in an electroscope

• What happens to the charges when you take the rod away?
• What is the net charge on the sphere ?
• Why negative charges are move away from the rod

Grounding

SLO: Describe conduction in an electroscope

• Flow of charges to the ground is called grounding.
• Earth can take any amount of charge.
• If the object is positively charge electrons will move from ground to the object.
• If the object is negatively charged the electrons will move from the object to the earth

Charging by induction

SLO: Describe conduction in an electroscope

Charging a sphere by induction

SLO:

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• Explain the process of induction.

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• Describe the process of induction in an electroscope.

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• Analyze Coulomb’s law and the factors affecting the electrostatic force

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Starter: Differentiate between friction and conduction

Lightning

• The negative charges at the bottoms of thunderclouds can cause the separation of charges on Earth.
• The forces between the charges in the cloud and those on Earth’s surface can break molecules in the air into positively and negatively charged particles.
• These charged particles are free to move, and they establish a conducting path from the ground to the cloud.

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SLO: Describe the process of lightning

Charging by induction

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• Process of charging a neutral object by bringing a charged object near it is called charging by induction.

SLO: Describe the process of induction

Charging by induction

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• Process of charging a neutral object by bringing a charged object near it is called charging by induction.

SLO: Describe the process of induction

Charging by induction

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• Process of charging a neutral object by bringing a charged object near it is called charging by induction.

SLO: Describe the process of induction

Grounding:

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• Which is the process of removing excess charge by connecting an object to Earth.
• Because Earth is very large, it can absorb great amounts of charge without becoming noticeably charged itself.
• When you ground a charged object, almost any amount of charge can flow to Earth.

SLO: Explain grounding

Charging by induction in an electroscope

Steps of charging an electroscope by induction

SLO: Describe the process of induction

Check your understanding:AFL

Electrostatic Force