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(a) With the help of a diagram describe in brief an activity to show that a magnetic field is produced by a current carrying circular coil. Draw a diagram to show the pattern of the magnetic field lines in this case.

(b) State the function of the earth wire in domestic electric circuits. Why is the metallic body of an electric appliance connected to the earth wire? Write the colour used for insulation of the earth wire.

Ans. (a) Magnetic field produced by a current carrying circular coil.
(i) A rectangular card board having holes is taken and a circular coil having large number of turns is
inserted in the cardboard. The coil should be inserted in the cardboard in such a manner that the
coil is normal to the plane of the cardboard.

(ii) The ends of the coil are connected in series with a battery, a key and a rheostat.

(iii) Then iron filings are sprinkled uniformly on the cardboard.

(iv) Now the key is plugged.

(v) On tapping the cardboard gently, the circular magnetic field lines near the current carrying loop are observed. On moving away from the circular loop, the concentric circles representing magnetic field lines become bigger and bigger. At the centre of the circular loop, the magnetic field lines are straight. Also See Q.12, 2004 (Outside Delhi). [Page P-10

(b) The earth wire is used as a safety measure for electrical appliances having a metallic body. e.g., electric press, toaster, table fan, refrigerator etc. The earth wire, which has insulation of green colour
is usually connected to a metal plate dug deep inside the earth near the house. The leaked current from the appliance passes directly to the earth through the earth wire. Actually a very heavy current flows
through the earth wire and the fuse of household wiring melts and cuts off the power supply.
The appliance having metallic body is connected to the earth wire as it provides a low-resistance conducting path for the current. Thus it ensures that any leakage of current to the metallic body of the
appliance keeps its potential to that of the earth, and the user does not get a severe electric shock.

Section B

Q. 17. Why are coal and petroleum considered to be non-renewable sources of energy? 1

Ans. Coal and petroleum are considered to be non-renewable sources of energy because these fuels were formed over millions of years and there are only limited reserves and if all the coal and petroleum gets exhausted, these can not be produced quickly in nature.

Science 2009 Question Papers Class X
Delhi		Outside Delhi		Compartment Delhi		Outside Delhi		Foreign
	Set 1 (PDF)		Set 1 (PDF)		Set 1		Set 1		Set 1 (PDF)
					Set 2		Set 2
					Set 3		Set 3