NCERT Class X Science Solutions: Chapter 13 – Magnetic Effects of Electric Current Part 2

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Question 6:

State whether the following statements are true or false.

  1. An electric motor converts mechanical energy into electrical energy.

  2. An electric generator works on the principle of electromagnetic induction.

  3. The field at the centre of a long circular coil carrying current will be parallel straight lines.

  4. A wire with a green insulation is usually the live wire of an electric supply.

Answer:

  1. An electric motor converts mechanical energy into electrical energy. (False)

  2. An electric generator works on the principle of electromagnetic induction. (True)

  3. The field at the centre of a long circular coil carrying current will be parallel straight lines. (True)

  4. A wire with a green insulation is usually the live wire of an electric supply. (False)

Question 7:

List three sources of magnetic fields.

Answer:

Three methods of producing magnetic field are as follows:

  • Magnetic field can be produced by placing a permanent bar magnet or a horse-shoe magnet at the place, where magnetic field is required.

  • Magnetic field is produced around a current-carrying straight conductor or a current carrying circular coil.

  • A very good method to produce magnetic field is due to flow of current in a solenoid.

Question 8:

How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.

Answer:

When current is passed through a solenoid coil, magnetic field produced due to each turn of solenoid coil is in the same direction. As a resu1t, the resultant magnetic field become very strong and uniform. The field lines inside the solenoid are in the form of parallel straight lines along the axis of solenoid. Thus, the solenoid behaves like a bar magnet. One end of solenoid behaves as a magnetic North pole while the other end behaves as the South Pole.

Result for north and south poles of a current

North and South Poles of a Current

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We can determine the magnetic poles formed in a solenoid. The end of the current-carrying solenoid, which attracts North Pole but repels South Pole of a bar magnet, is behaving as south magnetic pole. The other end, which attracts South Pole of a bar magnet but repels the North Pole, is behaving as north magnetic pole. It is because like poles repel but unlike poles attract each other.

Question 9:

When is the force experienced by a current–carrying conductor placed in a magnetic field largest?

Answer:

The force experienced by a current-carrying conductor placed in a magnetic field is largest when the current-carrying conductor is placed in a direction perpendicular to that of magnetic field.

Question 10:

Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?

Answer:

An electron beam moving horizontally from back wall towards the front wail is equivalent to a current flowing in the opposite direction (i.e., from front wall towards the back wall). The deflection of electron beam as seen by observer is to his right side and is shown in Figure. On applying Fleming's left-hand rule we find that the magnetic field is acting in vertically downward direction.

Diagram shows Fleming's left-hand rule

Fleming's Left-Hand Rule

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