Anand Classes

ANAND CLASSES

# MODERN ELECTRON THEORY

An atom consists of a central part called nucleus and around the nucleus (called extra-nucleus) there are a number of electrons revolving in different paths or orbits.

The nucleus contains protons and neutrons. A proton is a positively charged particle while a neutron has no charge. Therefore, the nucleus of an atom bears a positive charge. An Electron is a negatively charged particle having negative charge equal to the positive charge on a proton.

Normally, the number of electrons is equal to the number of protons in an atom. Therefore, an atom is neutral as a whole; the negative charge on electrons cancelling the positive charge on protons. This leads to the conclusion that under ordinary conditions, a body is neutral, i.e. it exhibits no charge.

# What is the nature of Electricity ?

Matter is electrical in nature, i.e., matter contains particles of electricity viz., protons and electrons. Whether a given body shows electricity (i.e., charge) or not depends upon the relative number of these particles in the body.

1. If the number of protons is equal to the number of electrons in a body, the resultant charge is zero and the body will be electrically neutral.For example, the paper of this book is electrically neutral (i.e., exhibits no charge) because it has the same number of protons and electrons.
2. If from a neutral body, some *electrons are removed, the protons outnumber the electons. Consequently, the body attains a positive charge. Hence, a positively charged body had deficit of electrons from the normal due share.
3. If a neutral body is supplied with electrons, then electrons outnumber the protons. As a result, the body acquires a negative charge. Hence, a negatively charged body has an excess of electrons from the normal due share.

# ELECTRIC CHARGE

When a body has deficiency or excess of electrons from the normal due share, it is said to be charged or electrified.
The study of atomic structure reveals that matter is electrical in nature, i.e., matter contains vast amount of electric charge (protons and electrons).

Under ordinary conditions, the body is electrically neutral because it contains equal amounts of positive and negative charges. When this equality or balance is disturbed by removing or supplying electrons, the body acquires a net charge.

The body will acquire a positive or negative charge depending upon whether electrons are removed from it or added to it.

# Define Electric Charge

It is the physical property of  matter that causes it to experience a force when close to other electrically charged matter.

This FORCE is due to the property called “charge”.

Electric charge can be defined as a fundamental property of subatomic particles that gives rise to the phenomenon of experiencing force in the presence of electric and magnetic fields.

# Explain Different Types of Electric Charge

Electric charge comes in two main types: positive and negative charges.

Positive charges are associated with protons, which are subatomic particles residing in the nucleus of an atom. They are represented by the symbol “+”.

On the other hand, negative charges are linked to electrons, which orbit the atomic nucleus and are denoted by the symbol “-“.

The distinction between positive and negative charges plays a vital role in comprehending the behaviour of electrically charged objects.

Opposite charges, such as positive and negative, attract each other, while like charges, such as positive and positive or negative and negative, repel each other.

1. Negative Charge: When an object has more numbers of electrons than protons, it means that the object has a negative charge.
2. Positive Charge: When an object has less number of electrons than protons, it means that the object has a positive charge.

It’s important to note that when an equal number of positive and negative charges are present, they cancel each other out, resulting in a neutral state for the object.

• Proton is said to have a positive charge.
• Electron is said to have a negative charge.
• Magnitude of a positive or negative charge is given as “e = 1.6×10-19C”.
• Unlike charges attract each other and like charges repel each other.

# Is Electric Charge a Vector Quantity?

No, electric charge is not a vector quantity; it is a scalar quantity.

Electric charge is a scalar quantity, i.e., it does not obey the laws of vector algebra. Since charges are of two types (positive and negative), the total charge on a body is the *algebraic sum of the charges located at different regions of the body.

For example, two charges of +4q and +2q on a body will add up to give a charge = (+4q) + (+2q) = +6q.

Similarly, – 6q and +2q on a body will be = (– 6q) + (+2q) = – 4q.

Thus, electric charge is considered a scalar quantity, despite having magnitude and direction.

# How to Measuring Electric Charge ?

Coloumb is the unit of electric charge.

“One coulomb is the quantity of charge transferred in one second.”

Mathematically, the definition of a coloumb is represented as:

Q = I.t

In the equation, Q is the electric charge, I is the electric current and t is the time.

In practice, coulomb is used as the unit of charge, i.e., SI unit of charge is coulomb abbreviated as C.

# What is Static Electricity ?

Static electricity refers to an imbalance between the electric charges in a body, specifically the imbalance between the negative and the positive charges on a body. The imbalance in the charge is introduced by physical means. One of the most common causes of static electricity is contact between solid objects. It was mentioned earlier that the movement of protons is not possible and the only movement of electric charge seen in static electricity is electrons.

Electrons in materials are held extremely loosely meaning that they can be exchanged through simple contact like rubbing.

Example :

The image below is an example of rubbing a glass rod with silk which causes static electricity.

When two objects are rubbed together to create static electricity, one object gives up electrons and becomes more positively charged while the other material collects electrons and becomes more negatively charged. We should keep in mind that the rules such as like charges repel and unlike charges attract is applicable here.

Other Examples :

Speaking of times when your hair seems to stand on its ends when you remove your cap. Static electricity is the culprit here as well. As you remove your hat, electrons are transferred from hat to hair, creating that interesting hairdo! Remember, objects with the same charge repel each other. Because they have the same charge, your hair will stand on end. Your hair is simply trying to get as far away from each other as possible!

The same is true for when you comb your hair repeatedly with a comb. If you bring a comb you have used close to small bits of paper you will see that the comb attracts the pieces of paper. The comb loses electrons while rubbing your hair and this charge imbalance creates static electricity which then attracts the small bits of paper.

This happens because the charged comb induces an opposite charge in the paper and as opposite charges attract, the paper sticks to the comb.

# Define Electrostatics

The branch of physics which deals with charges at rest is called electrostatics.
When a glass rod is rubbed with silk and then separated, the former becomes positively charged and
the latter attains equal negative charge. It is because during rubbing, some electrons are transferred from glass to silk. Since glass rod and silk are separated by an insulating medium (i.e., air), they retain the charges.
In other words, the charges on them are static or stationary. Note that the word ‘electrostatic’ means electricity at rest.

## What is an electric charge?

Electric charge or charge is the fundamental physical property of matter that causes it to experience a force when kept in an electric or magnetic or electromagnetic field.

## How is the electric charge classified?

Electric charges are classified as positive charges and negative charges.

1. Negative Charge: When an object has more numbers of electrons than protons, it means that the object has a negative charge.
2. Positive Charge: When an object has less number of electrons than protons, it means that the object has a positive charge.

## What are positive electric charges are called?

Positive electric charges are known as protons.

## What is an electron?

The electric charge, which is negatively charged, is known as an electron.

## Write Symbol and Define Unit of Electric Charge

The symbol ‘Q’ or ‘q’ is used to denote Electric Charge and Coulomb (C) is the SI unit of charge. The amount of charge that is passed through the cross-section of an electrical conductor in one second when the current has a value of one ampere is known as coulomb.

## How many electrons have an electric charge of 1 Coulomb ?

1/1.6 x 10-19 or 6.25 x 1018 number of electrons have an electric charge of 1 Coulomb.

True.

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