Question

An electric bulb is rated 40W at 220V. How many bulbs can be connected in parallel with each other across the two wires of 220V line if the maximum allowable current is 6A?

Answer 1

this the process to find it

Answer 2

Answer:

33 bulbs

Explanation:

Given:

V = voltage rating of each bulb = 220 V

P = power rating of each bulb = 40 W

v = voltage supply = 220 V

i = total desired supply current = 6 A

Assume:

I = current consumed by each bulb

Let us find out the current consumed by each bulb.

Using the relation between the power, current and voltage, we have

$P=VI\\\Rightarrow I =\dfrac{P}{V}\\\Rightarrow I =\dfrac{40}{220}\ A$

Let us first assume that n such bulbs are required.

We know that the resistance of each of the bulbs of this rating will have the same resistance. So, the current consumed by each of them when connected in parallel to a potential difference will be the same.

Moreover, the sum of the current supplied to each bulb will be equal to the total desired supply current from the source of 220 V.

$\therefore i = nI\\\Rightarrow n = \dfrac{i}{I}\\\Rightarrow n = \dfrac{6}{\dfrac{40}{220}}\\\Rightarrow n =33$

Hence, 33 such bulbs should be connected to 220 V source such that maximum allowable current is supplied.