STD IX – ELECTRICITY AND MAGNETISM – (Online)

ELECTRICITY

ELECTRIC CURRENT:

Some common terminology used in this lesson.

Current: It is defined as the rate of flow of charge.

Conductors: Substances that allow current to flow through them. Example, metals such as copper, aluminium, silver, iron, etc.

Insulators: Substances which do not allow the current to flow through them. Example, cotton, rubber, plastic, wood, paper, etc.

Circuit: The path along which the current flows is called a circuit.

Potential Difference: The potential difference (p.d.) between two points is equal to the work done in moving a unit positive charge from one point to the other.

Resistance: The obstruction offered to the flow of current by the conductor (or wire) is called its resistance.

MAGNETISM

Induced Magnetism and Neutral Points

Magnetism affects magnetic materials and electric currents. The effect of a permanent magnet on ferromagnetic materials is so strong, that a ferromagnetic material can be magnetised to become a permanent magnet. For example, iron, nickel, cobalt etc.

Terms associated with magnets and magnetism:

Magnetic Poles

Induced Magnetism

Magnetic Field of Earth

Neutral Points

ELECTROMAGNET

Electromagnet and its Uses

Humans all over the world have known about magnets for more than 3000 years in the form of naturally occurring magnets called lodestones. Lodestones are magnetised material of the magnetite ore that can attract iron.

The word magnet comes from the Greek phrase, ‘magnitis lithos’, which means a stone from the land of Magnesia.

Even the properties of a magnet have been discussed by the Greeks, Chinese and Indians from around 600 BC, it was from the 11^th century onwards its use began, mostly in a compass to find direction.

A magnet is able to attract or repel another magnet or a magnetic material. This magnetic effect of one magnet on another magnet or on a magnetic material is magnetism.