Basic Properties of Electric Charge for JEE Main

In a general terminology, electric charge is the amount of energy or electrons that pass from one system to another system. This transfer can be mediated by different mechanisms such as conduction, induction, or other specific methods. Electric charges are divided in two categories namely positive (+) charge, and negative charges (-). Charges are present in almost every system. However, several systems do not have charges, either have no charge or have neutral charge. 

What is an Electric Charge?

Protons, electrons, and neutrons are examples of the basic subatomic particles, in which protons possess positive electrical charge, electrons possess negative electric charge and neutrons have neutral charge. The symbol of charge is ‘q’ or ‘Q’. The total charge of electrons present in an atom is the number of electrons multiplied by the charge of an electron. According to this definition, the formula for charge can be written as,

Q = ne,

Where Q is a charge, e is charge on one electron, and n is the number of electrons. It is possible to measure the charge of a body by comparing it to a standard value. According to a study, the charge of electrons is 1.6 x 10-19C. The S.I. unit or Standard unit of electric charge is Coulomb and it is denoted by ‘C’.

Definition of 1 C:

If the current flowing through the wire is 1 A, then 1 C can be defined as the charge flowing or passing through a wire in 1 second.

There are very two basic properties of electric charge. They are: 

• Similar electric charges tend to repel each other.

•  Opposite electric charges tend to attract each other.

For example, two protons, and two electrons repel each other. In the case of protons and electrons, they tend to attract each other. These properties depend on the nature of charge i.e. the force acting on them and coordinating the direction of flow. The proton and electron possess the same amount of charge but they are opposite in nature. (Note: The charge of protons is 1.6 x 10^-19 C, whereas the charge of electrons is -1.6 x 10^-19 C.) The difference is the type of charge they carry.

Basic Properties of Electric Charge

There are certain basic properties of electric charge that they follow. The electric charges are considered as point charges if the size of the electrically charged bodies is so small. Apart from the above-mentioned properties of electric charge, there are certain other basic properties they possess. They are:

1. Additive property of electric charge

2. Conservative nature of charge

3. Quantization of charge

 In this section, these properties are described in detail.

1. Additive property of electric charge

Electric charges are additive in nature, and it depends upon the type of electric charge they carry. It is a scalar property. It is possible to add them directly. For example, let us consider a system containing only two charges, namely q1 and q2. According to this property, the total charge of the system can be calculated by an algebraic sum of q₁ and q₂ i.e. q₁ + q₂. Similarly, the same thing holds if there are more than two electric charge particles. Suppose, a system contains q₁, q₂, q₃, q₄ ………. q_n, then the net charge of the whole system can be calculated by summation.

Net Charge = q₁ + q₂ + q₃ + q₄ + ……. + q_n

2. Conservative nature of electric charge

Electric charge of a particle is conservative in nature. It means that the charge can neither be created nor be destroyed. The charges can be transferred from one system to another system by mechanisms like conduction, and induction. It is similar to the law of conservation of mass and also, similar to the first law of thermodynamics (i.e. law of conservation of energy). Rubbing of two bodies involves a transfer of electrons from one body to another.

For example, let us consider a system containing a total of 10C charge. It is possible to redistribute that charge as 2C, 3C, and 5C or it is also possible to redistribute it according to any other possible permutation. Sometimes several systems tend to lose an equal number of protons and electrons. Hence, the final charge of the system would be having exactly similar charge as it was present initially. This condition is seen in neutrino decay. During the decay, a neutron loses one electron and one proton. Ultimately, the total charge of the system will be zero as it loses electrons and protons of the same magnitude and opposite signs. 

3. Quantization of Charge

 The charge of a system is a fixed quantity. Technically, the charge is a quantized quantity. The net charge of a system can be expressed as the integral multiples of the basic unit of charge (i.e. 1.6 x 10^-19 C. Suppose, the net charge of the body is q, then it can be written as:

q = ne

In this formula, n represents an integer number and it can not be a fractional or irrational number. So, the value of n can be any positive or negative integer. For example, the value of n can be 1, -1, 2, -3, 4, -5 etc. The symbol ‘e’ represents the basic unit of the charge that is carried by electrons and/or protons. Conventionally, the charge on protons is simply denoted as ‘e’, while the charge on electrons is denoted as ‘-e’. 

The principle of the quantization of electric charge was first proposed by English scientist Faraday. This proposal was based on his experimental laws of electrolysis, and in 1912, this principle was demonstrated and proved by Millikan.

It was reported that 1 A Coulomb of charge has around 6 x 10¹⁸ number of electrons. In general, particles do not have a high magnitude of charge, and hence, the smaller units of coulomb are generally used in routine practice. Commonly used units for electric charge are micro-coulomb or milli-coulomb.

Micro coulomb can be denoted as ‘μC’ and milli coulomb is denoted as ‘mC’. The conversion factor from milli coulomb to coulomb is:

1 mC = 10^-3 C

Similarly, the conversion factor from microcoulomb to coulomb is:

1 μC = 10^-6 C

The concept of quantization of electric charge is very important to calculate the total amount of electric charge present in a system by using equation ‘q = ne’. Suppose, for example, a system has a total n1 number of electrons and total n₂ number of protons. Then, based on these properties, we can say that the total amount of charge can be represented as n₂ e – n₁ e.

 Net amount of charge = n₂ e – n₁ e

 OR

 Net amount of charge = (n₂ – n₁) e

Solved Example using Above-mentioned Properties

Problem 1: A system is made up of 6 subatomic particles, in which there are 4 protons, and 2 electrons. The charges present on these six particles are + 2C, + 4C, + 10C, + 6C, - 4C, and – 2C. Calculate the net charge present within the system.

Solution: 

According to the property of electric charge, the net charge of a system is an algebraic sum of a charge of an individual subatomic particle. 

Consider the total charge or net charge of the system as ‘Q’. Then, according to the addition of property of electric charge:

Total charge of the system Q = 2 C + 4 C + 10 C + 6 C + (- 4 C) + (- 2 C)

 Q = 16 C

Hence, the net charge of the system would be 16 C.

Problem 2: A system is made up of 10 subatomic particles, in which there are 4 protons, and 2 electrons and 4 neutrons. The charges present on these six particles are + 2C, + 4C, + 10C, + 6C, - 4C, and – 2C. Calculate the net charge present within the system.

Solution:

As we know, the charge present on one proton is e and the charge present on one electron is -e, as well as, the charge present on neutrons is zero and it does not depend on the number of neutrons present in the system.

According to the property of electric charge, the net charge of a system is an algebraic sum of a charge of an individual subatomic particle. 

Consider the total charge or net charge of the system as ‘Q’. Then, according to the addition of property of electric charge, 

Total charge of the system Q = 2 C + 4 C + 10 C + 6 C + (- 4 C) + (- 2 C) + 0 + 0 + 0 + 0

Q = 16 C

Hence, the net charge of the system would be 16 C.

Thus, we can state that:

1. Electric charge is the amount of energy or electrons that pass from one system to another system.

2. Electric charges are divided in two categories namely positive (+) charge, and negative charges (-).

3. Charge is a scalar quantity. It has a specific magnitude and no direction.

4. Charge is a conserved quantity.

5. Similar charges repel, while opposite charges attract each other.

Basic Properties of Electric Charge for JEE Main and How to study it?

Understanding and comprehending the basic properties of electric charge was made swift for the students through the above content. Some of the solved questions must also have allowed you to brainstorm and apply the knowledge that you've gained. 

Since it is about clearing a competitive exam, you might also need a detailed explanation and ample practice. For that, you might visit the Vedantu website or download the app so that you can prepare better. Exams of such levels come with a lot of uncommon behaviours, most of which are anxiousness and pressure. When your inner voice takes over, you might have always wanted to be silent and try it out for yourself by figuring out the best ways to be able to do it. 

Let's understand some of the ways that can be used to overcome procrastination.

• Create a favourable environment 

Creating a favourable environment means eliminating what distracts you and stops you from taking action. Whether it’s about the gadgets or lack of a proper study place. For some students, too much motivational stuff around them also demotivates them because they experience questions of self-doubt and on the other hand, for some of them, it may act as fuel to them. To be able to truly figure out what works out best for you is to be able to observe your habits and patterns and based on that, optimize your learning environment.

• Redefine your plan 

There may be many times that you might want to realign your plan and that is why you need to observe the schedule that you've made for yourself and make relevant changes. This will help you to rethink everything and in the long run, your targets would be more achievable and realistic which would finally help you to succeed.

• Focus on ‘why’ 

The ‘why’ behind every goal is the reason that fuels you to take action. Whenever you’re low on motivation and are spending too much time just thinking about how and where to start from, you shall be able to visualise your end goal in a larger perspective. This allows you to refocus and put yourself into action.

• Acknowledge your Achievements 

Students shall understand that as much as it is important to consider their mistakes, it is also important to acknowledge and keep a record of your achievements, even the smallest ones. This allows you to stay motivated and focused. Don't be harsh on yourself, be consistent and keep moving ahead and that's how you will get where you want to land.