Magnetism

Magnetism

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​See how each pin turns into a magnet itself attracting the other pin

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Natural & Artificial magnets

Kinds of Artificial MAgnets

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Properties of Magnets

Magnet attracts small pieces of iron towards itself

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A freely suspended magnet rests in the north-south direction

Similar poles repel and dissimilar poles attract each other

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Open Ended

On bringing two pieces together they attract each other, can you say both pieces are magnets?

Multiple Choice

A surer test of magnetism is

• Attraction

• Repulsion

Magnets can magnetise pieces of iron

ICSE Syllabus for Magnetism

Induced magnetism, Magnetic field of earth. Neutral points in magnetic fields. Magnetism: magnetism induced by bar magnets on magnetic materials; induction precedes attraction; lines of magnetic field and their properties; evidences of existence of earth’s magnetic field, magnetic compass. Uniform magnetic field of earth and non-uniform field of a bar magnet placed along magnetic north-south; neutral point; properties of magnetic field lines. 

Magnetic Induction

The magnetism acquired by a magnetic material when it is kept near (or in contact with) a magnet, is called induced magnetism.

MAgnetic Induction

The process in which a piece of magnetic material acquires the magnetic properties temporarily in presence of another magnet near it is called the magnetic induction.

When a piece of iron is placed near or in contact with a magnet, the piece of iron becomes a magnet i.e., it acquires the property of attracting iron filings when they are brought near its ends. Thus, a piece of iron behaves as a magnet as long as it is kept near (or in contact with) a magnet.

​Magnetic Induction

Electric method of Magnetisation

Open Ended

Why would you make and use an electromagnet if bar magnets are already available?

Multiple Choice

Is magnetic force a contact force

• yes

• no

The magnetic field of a bar magnet

The magnetic field due to a magnet is represented by magnetic lines of force

Plotting magnetic lines of force for a bar magnet

Properties of Magnetic Lines of Force

Magnetic field lines emerge from the north pole and merge at the south pole.

As the distance between the poles increases, the density of magnetic lines decreases.

The direction of field lines inside the magnet is from the South Pole to the North Pole. Magnetic lines do not intersect with each other.

The strength of the magnetic lines is the same throughout and is proportional to how close are the lines.

Earth's Magnetic field

Plotting of Earth's magnetic field lines

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Multiple Choice

The Earth's magnetic field in a small region such as a laboratory or even a city is uniform

• yes

• no

Plotting magnetic lines of force

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Multiple Select

What will happen if a magnetic compass is taken away from a magnet

• magnetic field increases so the compass deflects strongly

• magnetic field decreases so the compass deflects gently

• the farther you go from the magnet the weaker is the magnetic field

• very far from the magnet the compass will rest in the N S direction

Neutral point

• A neutral point is a point at which the resultant magnetic field is zero. In general, the neutral point is obtained when the earth's magnetic field is balanced by the magnetic field of a magnet.

Bar magnet's magnetic field in Earth's Magnetic field

When North pole faces the Geographical North pole

Bar magnet's magnetic field in Earth's Magnetic field

When the South pole faces the Geographical North pole