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Electric Fields
This section covers electric fields, problem-solving techniques, and explanations.
Electric charges cause attraction (pulling) or repulsion (pushing).
Examples of electric charge in experience include static cling, conduction, and induction.
Focus on experiments related to charges by conduction or induction.
The distribution of charge on a conductor of various shapes is explored.
How lighting is formed is explained.
The use of Van de Graaff generators to make a fluorescent tube glow is explored.
Electric Forces and Fields
This section defines the electric field.
Represent an electric field with field lines that originate on positive charges and end on negative charges.
Distinguish between the electric field inside and outside of conductors.
Note Coulomb's Law.
Compare Coulomb's law and Newton's law of universal gravitation.
Calculate the force acting on a charge due to another charge placed on the same plane (line of action).
Calculate the force due to three charges placed on a line.
Calculate the electric field strength at a point due to charges placed on a line at right angles.
Electric Potential
Section defines electric potential and its S.I. unit.
Distinguishes between absolute potential and potential difference.
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Explanation of equipotential lines and surfaces.
Drawing equipotential lines and surfaces in an electric field.
Defines electric potential energy.
Capacitors and Capacitance
Describes structure of a simple capacitor.
Defines the term capacitance and its S.I. unit.
Apply the definition of capacitance to solve numerical problems.
Use the circuit symbol to represent a capacitor.
Explains the charging and discharging of a capacitor.
Defines the term dielectric and explains what it's meant by a dielectric material.
Understanding the construction of capacitors in series and parallel.
Explains the effect of inserting a dielectric in the gap between the plates of a parallel plate capacitor.
Electrostatics - Unit 2
Electric Charge
Summary of the section to be learned to the electric charge.
Describe and explain the charging processes; Charging by rubbing, conduction, and induction.
Perform an experiment to charge an electroscope by conduction and by induction.
Describe the distribution of charge on a conductor of various shapes.
Explain how lighting is formed
Describe the use of a lighting rod
Explain how equipment stores using electrostatic principles
Electrostatics in everyday life
Electroscopes in an Everyday Life
Faye wants you ever felt a small electric shock when you have touched a metal door handle, or the held a crackling sound as you pull a woolen article of clothing over your head? Both of these arise because of electrostatics, the electric charge is transferred from one material to another.
In this unit you will learn more about this, its application and its hazards.
All objects are made up from tiny building blocks called atoms.
Individual atoms are made up of particles that possesses both mass and electric charge.
A material such as PERSpex is made up of contents Section dealing with concepts derive an expression for the effective. capacitance of capacitors connected in series and parallel.
Draw an electric circuit diagram for a simple capacitor series and parallel connectivity of two or more capacitors using symbols.
Problems on combination of capacities.
Define parallel plate conductors.
Describe the factors that affect the capacitance of a parallel plate conductor.
Calculate the capacitance of a parallel plate conductor.
Find an expression for the electrical potential energy stored in a capacitor.
Calculate the energy stored in a capacitor using the appropriate formulas.
Notes some of the use capacitor in everyda life example.
Van De Graaff Uses
Electrostatic - the build-up of electric charge on the surface of objects.
Charge in an electric charge, positive, negative or zero.
Particles of matter - atoms (the smallest components of an element) have the chemical properties of that element.
Positive charge having a negative charge having number of electrons.
Recall other physical quantities that are considered.
In a small group spend one minute writing a list of physical quantities that you have met that follow a conservation law. Hint: think back to Unit 1.
Conservation of Charge
Number of atoms although very varied, are very small relative to mass, it does not seem to possess any charge at all.
Every bit of mass in every atom adds up so that we feel its mass.
If in a single atom, however, the two sorts of electric charge canceled one another out, there is the same number of positive charges as negative ones so we do not notice any overall charge.
An uncharged piece of PERSpex contains a vast number of charges, but the numbers of two kinds are equal.
Charging it involves upsetting the balance between positive and negative charges.
Adding or removing a few more electrons would do this.
$e = 1.6 \times 10^{-19} \, C$. is the amount of charge in an electron (negative charge ) or on a proton (positive charge ).
So, you use $Q= N e $, where N is the number of electrons.
Conservation of Charge
Number of positive charges on an atom is the same as the number transferred to another material in the process known as charging.
But everall number of positive and negative charges does not laws of conservation of charge.
Like charges will repeal each other (for example, 2 positive charges will both repel each other, 2 negative charges will both repel each other).
Unlike charges will attract each other (so a positive charge will attract a negative charge and vice versa).
Charging Materials by Rubbing
It is possible to charge some materials by rubbing them.
When you rub a piece of PERSpex, for example, some of the charge is transferred from the surface of the PERSpex to the material you are using to rub it, and so the overall charge on the PERSpex becomes unbalanced.
Activity 2.2 Testing how charged bodies attract or repel one another
Take a bar of PERSpex and pivot it.
One way is to suspend it by a nylon thread (cotton, if the slightest bit damp, may allow all charges to leak off too rapidly).
Charge the suspended rod by rubbing it.
Bring a second charge PERSpex rod up to the first one and you will see the first one swing away.
Now charge the bar of polythene up to the suspended rod , and you will see the suspended rod moving towards it.
What do these tells you about the charges on the PERSpex and the polythene? Climate standard.
Climate Perpex rod nylon tread
Figure 2.2 Apparaturs to test attraction or repulsion between charged bodies.
Rubbing Perspex transfers charges from the surface of the Perspex to the material you are rubbing it with.
And with that
DED Internal Assessment (such as a Member ) Becomes Rubbed Has Been Known
Activity 2.3 : Handling Balloons Using Electrostatic Attraction.
Inflate a balloon and then briskly rub one side of it on your hair.
Place the surface that you have rubbed towards a wall or door and release it when it appears to be sticking. What can you say about the nature of the surfaces to which the balloon sticks?
Figure 2.4 Rubbing a balloon on hair.
Figure 2.5 A balloon sticking to a surface.
Charging Materials by Conduction
If the charged object is brought into contact with the uncharged object, then the neutral object will become charged by conduction.
You touch a metal door handle and the door handle has become charged and the charge transfers by conduction to you, a neutral object.
Figure 2.6. Charging a person by conduction.
Activity 2.5 The Electrostatic Attraction of Water
Adjust a tap so that a continuous but gentle stream of water is falling from it.
Rub a plastic comb on your sleeve and bring it up to the side of the water column.
Describe and try to explain what happens!
Figure 2.7 The attraction of water.
Comb Tap Running Stream of Water
There are questions to be asked, they include:
Activity 2.6 charging in Electroscope by Conduction
From the information given above about charging by conduction, device and carry out an experiment to charge in Electroscope by conduction. Draw diagram to explain what is happening!
DED Uses
As an electroscope is used to detect the presence and magnitude of the electric potential. Gold Leaf Electroscope is when leaves called the varistor, instrument Figure 2.9