# ELECTRIC CHARGE & COULOMB’S LAW

Q1: Define and explain electric charge hence differentiate between conductors and insulators?

## ELECTRIC CHARGE

The strength of electrical interacting of a particle with objects around it depends on its electric charge. Charges with same sign repel each other and charges with opposite sign attract each other. The object with equal amounts of the two kinds of charge is called electrically neutral. The object with an unbalance amount of the two kinds of charge is called electrically charged.

All materials including solids, liquids, and gasses contain two basis particles of electric charge called electrons and protons. The electron has negative polarity whereas proton has positive polarity.

It is the arrangements of electron and protons that determines the electrical properties of all the substances. The material that losses the electrons is called positively charged. The material that gains the electrons is called negatively charged.

### EXAMPLE,

The rod gets positively charged when it is rubbed against the silk whereas silk is charged negatively.

## UNIT OF CHARGE

The SI unit of charge is called coulomb. The charge of 6.25 ×10 electrons or protons is equal to one-coulomb charge. The submultiples units of charge are uC, nC and pC, etc.

## TYPES OF CHARGES.

The charge has two types called a positive charge and a negative charge.

1:  The similar charges repel each other with electric force.

2: The, unlike charges, attract each other with electric force.

## POLARITY OF CHARGE.

The charges of the same polarity repel each other while charges of opposite polarity attract each other. The positive and negative labels to charged materials are arbitrary and assigned by the Franklin.

## CHARGE OF ELECTRON.

The magnitude of the charge on an electron is 1.6 ×10 C, it is measured by Milliken.

## CHARGE OF NEUTRON.

The neutron has no charge, its mass is approximately equal to the mass of a proton.

## POLES OF CHARGE.

The charge forms poles.

1: An isolated single charge is called an electric monopole.

2: Equal positive and negative charge having a constant separation between them is called electric dipole.

3: The oppositely directed dipoles close to each other are called an electric quadrupole.

You can continue the process to any number of poles, but dipoles and quadrupoles are important because they find significant application in the physical phenomenon.

## CONDUCTORS.

THE materials through which charges can flow easily are called conductors. Some properties of conductors are.

1: The copper and aluminum are good examples of conductors.

2: The free electrons are mobile and positive ionic cores are immobile within the conductor.

## ELECTRIC FIELD

Q1: Define and explain the electric field in detail?

### Electric Field

The space or region around a charge in which attraction or repulsion with other charges takes place is called electric field.

The charges produce an electric field which is denoted by dots. The density of dots is proportional to the strength of the electric field. The presence of the field is tested by the test charge. The test charge is generally +q

Consider a charge q which produces an electric field. The electric field of charge q interacts with test charge q and gives rise to the electric force. The electric force per unit test charge is called electric field intensity.

E = F/q electric field in intensity

## DIRECTION OF ELECTRIC FIELD LINES.

The electric field is a vector quantity and electric field lines give its direction the electric field lines come out from positive charge and enter into negative charge. The two electric field lines never cross each other.

## UNIT,

The SI unit of the electric field is called N/C or V/m.

Q2: What are electric field lines of force? How are these lines drawn? Write their properties?

## ELECTRIC FIELD LINES

The electric field lines are a map which provides information about the direction and strength of the electric field at various places. The concept of electric field lines was introduced by Faraday…

Consider a+q charge is placed at the center of the sphere. Now, +q0 test charge placed at any point on the surface of the sphere is repelled outward in radius direction Hence, the electric field comes out from positive.

Now place __q charge at the center of the sphere. The test +q0 is placed at any point on the surface of the sphere is attracted towards negative charge. Hence, electric field lines are…

The map of electric field lines also provides information about the strength of the electric field. The field is stronger near the charge where field lines are closer to each other.

The field lines away from charge spread out and indicating a continuous decrease in the field strength.

The number of lines per unit area passing perpendicularly through an area proportional to the magnitude of the electric field.

The electric field lines associated with two identical positive charges are curved and seen to repel each other. The middle region shows zero field location called the neutral zone.

The behavior of electric field lines of two identical negative charges is also exactly the same. The field lines are curved which enter into region shows zero field location called neutral zone.

The electric field pattern of two opposite charges of the same magnitude is shown fig. The field limes start from positive charge and end on a negative charge…

The direction of resultant intensities is given by the tangents drawn to the field lines at particular points.

## PROPERTIES OF ELECTRIC FIELD LINES.

• The properties of electric field lines are as under…
• The electric field lines originate from positive charge and terminate on a negative charge.
• The tangent to an electric field line at any point gives the direction of the electric field at that point.
• The electric lines are closer where the electric field is strong…
• The electric lines are farther apart where the electric field is weak.
• Two electric lines of force never cross each other because E has only one direction at any given point. If the field lines cross E could have more than one direction