Electric Charge

Objective

• To understand about electric charges & its transfer by friction

Electricity

Electricity

Static electricityCurrent electricity

Static electricity

• Also known as electrostatic charges

• Generated due to friction.

Where do charges come from?

Matter is made up of atoms.

++

+

–

––

+

–

Proton (positive charge)

neutron (neutral)

electron (negative charge)

atom nucleus

Charge

• The electron is negatively charged.• The proton is positively charged.• The neutron has no charge, it is neutral.

If electrons = protons neutral

Where do charges come from??

If electrons > protons gaining electrons, negative charge

If electrons < protons losing electrons, positive charge

How do charges behave?

• Like charges repel; unlike charges attracts.

• A charged object may even attract a neutral one.

Examples

• When a polythene rod is rubbed with a woolen cloth, electrons transfers from the wool to polythene. So the polythene get a net negative charge & wool gets positive charge

Conductors , Insulators & semiconductors

CONDUCTORS INSULATORS SEMICONDUCTORS

They are materials that allows heat & electrons to pass through it

They don’t allow heat & electrons to pass through it

They are poor conductors when cold ,but much better conductor when warm

Electrons are loosely held in conductors

Electrons are tightly packed in insulators

They are ‘in-between’ materials

Eg: metals Eg: plastic, wood Eg: silicon, germanium

Earthing • If charges build upon materials, electrons

may be pulled through the air and causes spark

• To prevent any danger due to this spark, the object can be earthed

• Earthing means the object is connected to the ground by a conducting materials so that unwanted charges flows away.

Electrostatic induction

1)Charging a Two-Sphere System Using a Negatively Charged Object

2)Charging a Two-Sphere System Using a Positively Charged Object

3)Charging(positively) a single sphere by induction

4)Charging(negatively) a single sphere by induction

Electrostatic induction • The production of a charge in an

uncharged body by bringing a charged object close to it is known as electrostatic induction.

• The charges that appear on the uncharged materials are known as induced charges

Electric field

• The region around the electric charges where another charge when placed will experience a force of attraction or repulsion is called an electric field

• the direction of electric field is from the positive charge to the negative charge

• Electric field is represented by imaginary lines called electric field lines.

Home work

• Write any 3 Dangers of static electricity