• Call Now

1800-102-2727
•

# Origin of charge, Properties of charge, Practice problems, FAQs

Our day-to-day life has been so much around electrical appliances. From fans, lights, refrigerators to electric trains, we can’t live without electricity. The electricity involves flow of charges. The charge is a physical quantity which can’t be seen but can only be felt. We need to understand the charge so that we can use it for our betterment.

Table of content:

• Origin of charge
• Properties of charge
• Practice problems
• FAQs

## Origin of charge:

Electrical nature is intrinsic in any object. Atomic structure consists of protons, neutrons and electrons. Proton and neutron have almost same masses, 1.673×10-27 kg and 1.67510-27 kg respectively. An electron is almost massless. It has a mass of 9.11×10-31 kg. Atom consists of a small and relatively massive nucleus at its centre containing protons and neutrons. Surrounding it there exists a diffuse cloud of orbiting electrons. Electron has a negative charge and the amount of charge is 1.6×10-19 C. The magnitude of charge on the nucleus i.e., in all the protons equals the magnitude of charge on the total electrons orbiting around it. Thus, an atom becomes neutral in charge.

Charge is a scalar quantity.

Dimension of charge is [AT]

SI unit of charge is Coulomb

## Properties of charge

The properties of charge are:

a. like charges repel each other and unlike charges attract each other.

b. a charged object attracts an uncharged object.

c. charge is a scalar quantity and can be of two types - positive and negative charges.

d. charge is quantised and a quantum of charge is equal to e=1.6×10-19C . Charge on anybody will be some integral multiple of e. It can never be in fraction.

So, for a body containing charge, the amount of charge will be q=±ne where, n is an integer.

e. during any process the net electric charge of an isolated system remains constant.

f. charge is additive in nature. Let’s take a body having ±n1e charge in it. Another body is having n2e charge. So, the total charge can be calculated as, (±n1e)+(±n2e)

g. charge is always associated with mass. Charge can’t exist without mass.

h. a charged particle at rest produces only an electric field.

i. a charged particle in an un-accelerated motion produces electric and magnetic field.

j. A charged particle in accelerated motion produces both electric and magnetic fields. Also, it emits energy in the form of electromagnetic waves.

## Practice problems

Q. A rod gets charged by another rod. The total charge contained is +32 μC. Comment on the excess/deficiency of electrons.

A. The charge in one electron can be taken as, e=-1.6×10-19 C

The rods have a charge of +32 μC. It means it has a deficiency of electrons.

The deficiency is number of electrons.

Q. A negatively charged object lies on the table. Another object is put nearer to it. It is observed that the second object is being attracted towards the first object. Comment on the nature of charge of the second object.

A. We know, like charges repel each other and unlike charges attract each other and a charged object attracts an uncharged object. So there lie two possibilities. One, the second object may be of opposite charge i.e., positively charged. Two, the second object may be uncharged.

Q. A box is placed on a table. It is noticed that the photographic plate around it gets affected. We know that the box contains charged particles inside. Describe their state of motion.

A. A charged particle at rest produces only an electric field. A charged particle in an un-accelerated motion produces electric and magnetic fields. When the charged particle is put in an accelerated motion, it produces both electric and magnetic fields. Also, it emits energy in the form of electromagnetic waves.

So, it is clear that the charged particle is in a state of accelerated motion.

Q. How does a charged object interact with another charged object? What if the second object is uncharged?

A. A charged object attracts another object if the second object has an opposite charge or uncharged. The charged object will repel another object only if the second object has a charge.

## FAQs:

Q. What is the amount of charge in an electron, proton, neutron?
A.
The charge in one electron is -1.6×10-19C

The charge in one proton is +1.6×10-19 C

The neutron is a chargeless particle. So, it has zero charge.

Q. Deduce the dimension of charge. Write its unit.
A.
Charge can be quantified as, charge= current×time

So, $\left[charge\right]=\left[current\right]×\left[time\right]={A}^{1}{T}^{1}$

The SI unit of charge is C or Coulomb.

Q. A charged object is at rest. Then it is made to move in unaccelerated motion. There are detectors nearby which can detect electric fields, magnetic fields and radiation. Comment on the detectors signal as caught by these activities.
A.
A charged particle at rest produces only an electric field. A charged particle in an un-accelerated motion produces electric and magnetic fields. When the charged particle is put in an accelerated motion, it produces both electric and magnetic fields. Also, it emits energy in the form of electromagnetic waves.

So, when the charged particle was at rest it should produce only an electric field. When it was in unaccelerated motion, it should produce both electric and magnetic fields. In any case it should not emit radiation or electro-magnetic waves.

Q. Prove, repulsion is the best method for the detection of a charged object.
A.
Repulsion is said to be the sure test to find whether an object is charged or not. It is because of the fact that attraction can occur between an uncharged body and a charged body due to induction. But repulsion can take place only between two charged bodies.

When a charged body is brought nearer to an uncharged body, the charged body induces an opposite charge on the part of the uncharged body nearer to it. This leads to attraction between the two bodies. It may give a false conclusion that the uncharged body is a charged body.

For repulsion to occur, both the bodies must carry a charge which is possible only if they are charged. Hence, the repulsion is the sure test to find whether an object is charged or not.

Talk to Our Expert Request Call Back
Resend OTP Timer =
By submitting up, I agree to receive all the Whatsapp communication on my registered number and Aakash terms and conditions and privacy policy