CBSE Class 10 Science Exam 2014 Term 1 Paper

Question : 14 of 36

Marks: +1, -0

A circuit has a line of

5 {\A}

. How many lamps of rating

40 {\W} ; 220 {\V}

can simultaneously run on this line safely?

Solution:

Given,

{\I}=5 {\A}

,
Let, No. of lamps be

n

, and
Power of each lamp

=40 {\W}

∴ \;\;

Power of

n

lamps

=40 n

watt
As,

{\P}\;= {\V} × {\I}

40 n\;=220 × 5

⇒ \;\; n\;=\;{220 × 5}/{40}=\;{55}/{2}

\;=27.5 ≈ 27

∴ \;\; \;\text " No. of lamps "\;\;=27

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