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Chapter 13 Magnetic effects of Electric Current

Electricity and magnetism were discovered independently but both are closely related. Magnets are commonly used nowadays in preparing floppies, credit cards, ATM, toys etc. In the field of medicine magnetic device i.e. Magnetic resonance imaging scanners are used to diagnose the patients. In this chapter we will study about magnets, its type, magnetic field, magnetic field line, electromagnet, electric motor, electric generator and many more.

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Exercise 1 ( Page No. : 224 )

Exercise 2 ( Page No. : 228 )

  • Q1 Draw magnetic field lines around a bar magnet.

    The region surrounding a magnet in which the force of a magnet can be detected is said magnetic field. On putting magnet filings around magnet the arrange in pattern representing magnetic field line. Magnetic field lines of a bar magnet emerge from the north pole and merge at south pole. Inside the magnet the direction of the field line is from south pole towards north pole.

    Q2 List the properties of magnetic field lines.

    The properties of magnetic field lines are: 

    (a) Magnetic field lines emerge from the north pole.

    (b) They merge at the south pole.

    (c) The direction of field lines inside the magnet is from the south pole to the north pole.

    (d) Magnetic lines do not intersect with each other.

    Q3 Why don’t two magnetic field lines intersect each other?

    Two magnetic lines never intersect because if two field lines of a magnet intersect, then at the point of intersection, the compass needle points in two different directions which is not possible at same time a needle shows to different directions. Hence, they never interact.

Exercise 3 ( Page No. : 230 )

Exercise 4 ( Page No. : 232 )

Exercise 5 ( Page No. : 233 )

  • Q1 State Fleming’s left-hand rule.

    Fleming’s left hand rule states that if we arrange the thumb, the centre finger, and the forefinger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the centre finger gives the direction of current, and the forefinger points in the direction of magnetic field.

    Q2 What is the principle of an electric motor?

    The principle of an electric motor is based on the magnetic effect of current. A current-carrying loop experiences a force and rotates when placed in a magnetic field. The direction of rotation of the loop is determined by Fleming's left-hand rule.

    Q3 What is the role of the split ring in an electric motor?

    The split ring in the electric motor is a commutator. The commutator reverses the direction of current flowing through the coil after each half rotation of the coil. Due to this direction of current getting reverse, the coil continues to rotate in the same direction.

Exercise 6 ( Page No. : 236 )

  • Q1 Explain different ways to induce current in a coil.

    The different ways to induce current in a coil are as following:

    a. If a magnet is moved relative to a coil, then an electric current is induced in the coil.

    b. If a coil is moved rapidly between the two poles of a horse-shoe magnet, then an electric current is induced in the coil.

Exercise 7 ( Page No. : 237 )

Exercise 8 ( Page No. : 238 )

Exercise 9 ( Page No. : 240 )