Class X Physics: Magnets and Magnetic Fields

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WHAT ARE MAGNETS?

1. A magnet is a piece of iron or other material which exhibits properties of magnetism, such as attracting other iron-containing objects or aligning itself in an external magnetic field.

2. Magnets have a magnetic field around them. Study of magnetic field helps us explain the properties of magnets.

3. With the use of electricity, we can create artificial magnet called electromagnet, which has a variety of use. Magnets are used in many gadgets; the earphone is just one of them. Here, we take up magnets, magnetic field, properties of magnetic field and electric motor

4. A bar magnet is a rectangular piece of iron, steel or magnetic material, that shows permanent magnetic properties.

5. A compass needle is a small bar magnet. The end pointing towards the north is called north seeking or north pole. The other end that points towards the south are called south seeking or south pole.

PROPERTIES OF MAGNETS

6. Magnets show the following two properties:

(i) like poles repel (north pole repels north pole and south pole repels south pole), while


(ii) unlike poles of magnets attract each other (north pole attracts south pole and vice versa)

WHAT ARE MAGNETIC FIELD?

7. The region surrounding a magnet, in which the force of the magnet can be detected, is said to its magnetic field. The iron filings when sprinkled around a bar magnet arrange themselves in a pattern. The iron filings experience a force. The force thus exerted makes iron filings to arrange in a pattern.

8. The lines along which the iron filings align themselves in a magnetic field represent magnetic field lines. Magnetic field lines are a pictorial representation of magnetic field around a magnet. You can also draw the field lines of a bar magnet using a small compass.

9. The magnetic field is a quantity that has both direction and magnitude (ie Vector quantity).

PROPERTIES OF MAGNETIC FIELD

10. Magnetic field lines have the following properties: –

 

 


(i) By convention, the magnetic field lines emerge from the north pole and merge at the south pole (look at the figure). Inside the magnet, the direction of field lines is from its south pole to its north pole. Thus, the magnetic field lines are closed curves.

(ii) The relative strength of the magnetic field is shown by the degree of closeness of the field lines. The field is stronger where the field lines are crowded (more field line per square unit/magnetic field lines are closer to each other).

(iii) No two field-lines cross each other. (If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.)

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