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Electric charges

This document discusses electric charges and static electricity. It explains that atoms are made up of protons, neutrons, and electrons. The proton has a positive charge, the electron has a negative charge, and the neutron is neutral. It also discusses how charges behave, with like charges repelling and unlike charges attracting. Static electricity is generated through friction, such as when a polythene rod is rubbed with wool, transferring electrons from the wool to the rod. Conductors, insulators, and semiconductors are compared in terms of how they allow electrons to pass through. Earthing and electrostatic induction are also summarized.

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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