Page 212 - NCERT Science Class 10 English Medium

E X E R C I S E S

1. Which of the following correctly describes the magnetic field near a long
straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
2. At the time of short circuit, the current in the circuit
(a) reduces substantially.
(b) does not change.
(c) increases heavily.
(d) vary continuously.
3. State whether the following statements are true or false.
(a) The field at the centre of a long circular coil carrying current will be
parallel straight lines.
(b) A wire with a green insulation is usually the live wire of an electric supply.
4. List two methods of producing magnetic fields.
5. When is the force experienced by a current–carrying conductor placed in a magnetic
field largest?
6. 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?
7. State the rule to determine the direction of a (i) magnetic field produced around a
straight conductor-carrying current, (ii) force experienced by a current-carrying
straight conductor placed in a magnetic field which is perpendicular to it, and
(iii) current induced in a coil due to its rotation in a magnetic field.
8. When does an electric short circuit occur?
9. What is the function of an earth wire? Why is it necessary to earth metallic
appliances?

Magnetic Effects of Electric Current 207

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