Static Electricity

Hello physicists, how have you been? today on physics we will be talking about,
static electricity a.k.a electrostatics - that is, production of electric charges.

Discovery Of Electric Charges

Experimental discovery shows that whenever two bodies are rubbed together, they acquire attracting property on some light objects such as paper. Consider one ebonite rod rubbed with a fur {hairy skin material}; they are seen to attract each other. The two bodies are said to be electrified and which other examples are glass and silk, that attracting force is called static electricity or electrostatics.

Explanation On How Electric Charges Are Produced

Let us consider two ebonite rods rubbed with fur and brought together, the two rod will be seen to repel each other. When a rod of ebonite rubbed with fur attract a glass rod rubbed with silk, it shows that electrification of the ebonite rod is different from the electrification of the glass rod, that is, different charges are present on both rods . These two different charges are called positive {+ve} charge and negative {-ve} charge. The glass rod is said to acquire positive {+ve} charge while the ebonite rod acquires negative {-ve} charge.
So in conclusion, positive charge of the glass is equal to the negative charge of the ebonite rod when brought together, hence, they attract each other through static electricity.

Law Of Electrostatic State That:

Like charges repel each other and unlike charges attract each other.

Ways To Experience Electric Charge

We have all experienced electric charge in our life, before you say no, you haven't, I need you to accept that, you have but you just don't know you did.

During the dry season{December - January} there is high circulation of charges because of the wind flow.
During this period, have you ever felt your body hair{especially your arm} rising up? if you haven't, what about when ironing your clothes, have you ever heard this cracking sound and faint sparkling? you should have had expreceince on any of the two above. But if not, simply pick up a pen, and use the bottom of the pen to rub your head {with some amount of hair} then after the rubbing, quickly place it on a small piece of paper, you will found out that, the pen attracts the piece of paper, just like a magnet {You will only see clear result during the dry season, because there are more charges}. What just happened is that, you just transfer some electric charges produced by static electricity from your head hair to the pen, so simply you made the pen to be able to attract the piece of paper.

Question : Between the piece of the paper and the pen, which one is positively charged and which one is negatively charged?

Answer : Yes, the pen is negatively charge because it attracts negative charge from the hair while the piece of paper is positively charged.

Electrostatic Or Static Electricity Induction

Electrostatic or Static Electricity induction is a method of charging a body by introducing a charged body to a neutral body and when this is done, the body is said to be induced with a or some charges.

How To Charge A Body Through Induction Process

From the word, Induce:
To charge a body, the neutral body A is made to stand on an insulator not on a conductor. A charged body B is introduced to the neutral body of A by electrostatic induction. The nearer side of A gets reversely charged while the further side gets similarly charged.
Observe the image below;

static electricity induction

When the charged body B is removed, the induced positive and negative charges are neutralized, showing no resultant charge.
Also observe the image below;

static electricity experiment

When the body is touched, the positive charge flows to the earth through the hand but the negative charge does not flow to the earth.
If the hand Is removed first, and then rod B is introduced, the whole surface will be bound with negative charge.

Observe from the experimental diagram below;

electrostatics induction of a neutral body

Note : Neutral body can be charged either positively or negatively, please note that.

Conclusion On How To Charge A Body Through Electrostatic Induction

To charge a body positively, a negatively charged rod is brought near and the neutral body, while to charge a body negatively, a positively charged rod is brought near.
That is all on production of electric charges through static electricity, how to charge a body with electrostatic induction, the law of electrostatic. Now let discuss about Gold-Leaf Electroscope

I believed you have all heard about Gold-Leaf before, but if not no worries. I will explain everything below;

Gold-Leaf Electroscope

Gold-Leaf Electroscope is an instrument that consists of a brass rod A and two gold leaves. The leaves are positioned parallel to each other and a metal disc B is attached to the end of the rod. This instrument is enclosed by outer and inner glass vessel C and a counter tin foil D is placed in the inner surface of the glass and the tin foil connected to the earth. {I believed you know what earth means in physics}.
Gold-Leaf electroscope is also an instrument for measuring, indicating and detecting charges. The tin foil diverges when there is a potential difference between the leaves; Note:</b this process measures the charge in the electroscope.
Below is the diagram of a Gold-Leaf Electroscope;

gold-leaf electroscope

How To Test Charges Using Electroscope Or Testing Of Charges By Electroscope

Using electroscope to test whether the charge on a body is positive or negative. The electroscope is first touched at the cap with a polythene strip, in order to make the charge negative and divergent.
A body with an unknown charge is brought near the metal disc of the electroscope and it diverges the unknown charge.

Note : Divergence, that is, repulsion is the only way to test for charge
below is the diagram for description;

when a polythene strip is brought near the Gold-Leaf Electroscope

That is when the polythene strip is brought near the Gold-Leaf Electroscope,
also observe the diagram below;

when unknown charged body is brought near the Gold-Leaf Electroscope after the polythene

When the unknown charged body is brought near the Gold-Leaf Electroscope after the polythene.

How To Charge An Insulated Body Or Charging In Insulated Body

A neutral insulated body is charged by bringing a positive charge close to an insulated body to be charged. Negative charges on insulated body are attracted towards the inducing charge while the positive charges are repelled away from it. The insulated body is earthed by touching it, so that the positive charge flows away, that is, conduct away.
Below is the diagram to the process;

charging an insulated body

phase two of charging an insulated body

Note that: The negative charge spreads round, leaving the body as a negatively charged.

Now let talk about conductors and insulators before we round it up on static electricity.

Conductors And Insulators

What is a conductor? Or what are conductors? any how;
Conductors are substances, mostly metals, that allows the passage of electricity through them.
Conductor can also be define as substance that can transmit heat, light, sound or electricity.
Examples of conductors are;
1} All metals
2} Human body, yes, we are a conductor.
What about insulator, what are insulators?
Insulator are substance, mostly non-metals, which do not allow the passage of electricity through them.
A more detailed definition of an insulator;
Insulator substance that does not transmit heat (thermal insulator), sound (acoustic insulator) or electricity (electrical insulator) or a non-conductive structure, coating or device that does not transmit sound, heat or electricity.

Examples of insulators are;
1} Wood
2} Plastic
3} Paper
4} Cotton

Distribution Of Charges On Conductors Or How Charges Are Distributed In Conductors

Experimental works have shown that charges are distributed where there is a sharp curve, that is, a sharp bend.
Note: The charge per unit area of a charged body surface is called surface density.
Surface density is greater at the corner or pointed edge than at the plain surface.
Check the below diagram for better understanding;

example of an equal charge distribution on conductors

That is an example of equal charge distribution, below is the other type of distribution.

charge distribution is greater at the sharp edge

Charge distribution is greater at the edge, that is, the sharp edge.

We are almost there guys, let quickly talk about lightning conductor and we rap it up on static electricity or let me just call it electrostatics, any one you prefer.

Lightning Conductor

Lightning conductor is used to prevent tall buildings from being damaged when struck by lightning. The conductor is a long metal rod installed or connected to the earth by means of a cable. The sharp outer point of the top gains an induced charge opposite to that in the thunder cloud. The charged ionizes the nearby air and the charged air molecules flow upwards from the point. This discharges the cloud before a lightning flash occurs.
This is the end of static electricity class session, ask your questions through the comment box. Enrol For This Physics Course to improve your skills in physics. Until next class, my name is Azeez Warith Olakunle

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