CBSE Class 10 Science Exam 2014 Term 1 Paper

Question : 22 of 36

Marks: +1, -0

(a) Draw magnetic field lines of a bar magnet. "Two magnetic field lines never intersect each other." Why ?
(b) An electric oven of

1.5 {\kW}

is operated in a domestic circuit

(220 {\V})

that has a current rating of

5 {\A}

. What result do you expect in this case? Explain.

Solution:

(a) Two magnetic field lines never intersect each other. The direction of magnetic field lines is always from north pole to south pole. If two magnetic field lines intersect, then it means that at that point of intersection the compass needle is showing two different directions of magnetic field which is impossible.
(b)

\;\text " Given : Power, "\;(P)=1.5 {\kW}=1.5 × 1,000

=1,500 {\W}

\;\text " Voltage, "\;( {\V})=220 {\V}

\;\text " We know, "\; {\P}= {\V} × {\I}

⇒ \;\; {\I}=\;{ {\P}}/{ {\V}}=\;{1,500}/{220}=6.8 {\A}

Now, the current drawn by the oven is 6.8 A which is very high but the fuse in this circuit has only

5 {\A}

capacity. When a very high current of

6.8 {\A}

flows through

5 {\A}

fuse, the fuse wire will get heated too much. As a result the fuse wire will melt and break the circuit thereby cutting off the power supply.

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