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The maximum number of 40W tube-lights connected in parallel which can safely be run from a 240V supply with a 5A fuse is: a) 5 b) 15 c) 20 d) 30
The maximum number of 40W tube-lights connected in parallel which can safely be run from a 240V supply with a 5A fuse is: a) 5 b) 15 c) 20 d) 30
CBSE | Class 10 | Lakhmir Singh | Magnetic Effects of Electric Current | Physics
The maximum number of 40W tube-lights connected in parallel which can safely be run from a 240V supply with a 5A fuse is: a) 5 b) 15 c) 20 d) 30

Answer:

The correct option is d) 30

Explanation
Let n be the number of parallel tube lights that can be safely run.
It is given that:
Power of one tube-light, $P =40 W$
Therefore, Power of $n$ tube-lights, $P=40 \times n$ watts
Potential difference, $V =240$ volts
Current, I = 5 amperes
We know that:
$$
\begin{aligned}
&P=V \times I \\
&40 \times n=240 \times 5 \\
&n=\frac{240 \times 5}{40} \\
&n=30
\end{aligned}
$$
A $240 V$ supply with a $5 A$ fuse can safely power 30 tube lights.

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