What is electric charge

Electric charge is an elemental character of matter due to which matter or object exerts electrical force in presence of another electrical force.

There are two kinds of electric charge, they are

1) Negative charge (-)

2) Positive charge (+)

Properties of electric charges

1)like charges repel each other. (for example one negative charge repels an another negative charge, similarly one positive charge repels an another positive charge)

 

2) Unlike charges attract each other (one positive and one negative charges are unlike charges, they always attracts each other)



      




From thousands of years people feels electric properties ,

Image A: when two glass rod rubbed with silk or wool cloth and one suspended in a silk thread, they start repelling one another. This is positive repels positive.

Image B: when two plastic rod rubbed with cat’s fur, they repel one another, this is called negative repelling negative.

Image C: But if one glass rod and one plastic rod are closer to each other they start attract one another, this is called positive attracts negative.

 

Gold leaf electroscope


This is used to detect the presence of charge on a body and it’s polarity.

1) Inside a glass vessel there is a vertical metal rod.

2)two very thin gold leaves are attached at the bottom end of the metal rod.

3) if a charged object touches the top end of the metal rod, electric charge flows through the rod to the leaves. As like charges repel each other, So the two leaves diverge.



4) More the charge on the object more diverge it will be, less divergence means less charges on the body.


Conductors: the objects or body which can conduct electricity or charge from one place to another are called conductors. For example metals are conductors, aluminium, copper, iron etc.

 

Insulators: the object or body which can not conduct electricity or electric charge from one place to another are called insulators. Example plastic, glass, wood etc.

 

Human and animal body are conductors.



If a charged body is connected or get touch with the earth surface all excess charges will be transferred from the body to the ground. This process  is  called grounding or earthing.

 

Earthing is safety process which is used to save houses, high buildings from dangerous lightening.

 

Earthing is also used in houses and electric circuits, if short circuits or any fault happens, current flows to the ground so that no harmful damage occurs or no human injury.

 

Charging by induction

In this process charging is carried out without touching one-another, so it is called induction.



1)two metal spheres A & B are touching one another and supported in two insulated stands as shown in the figure (1)

 

2) A positively charged rod is bring closer to the sphere A ()but no touching)




3)As we know positive charge attracts negative charge, electrons which are negatively charged are aggregate to the sphere A, and equal amount of positive charge also aggregate at the sphere B.

 

4)Now the sphere B is slightly do separated from the sphere A, in presence of positively charged rod keep closer to the sphere A as shown in the figure 


5) Now the positively charged rod is removed and sphere A and Sphere B are completely separated.



6) At the end of this process sphere A will be negatively charged and B will be positively charged in equal amounts.

7) This process of charging is called charging by induction.