. Several electric bulbs designed to be used on a 220 V electric supply line are rated 10 W each


How many bulbs can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A

Best Answer

First we will calculate the resistance R of one bulb

We know, P = V2/R

R = V2/P = 220V×220V/10W = 4840 Ω

Therefore, resistance of one bulb is 48400 Ω

We will now calculate the total resistance of the circuit by using Ohm's Law:

Thus, from Ohm’s law.

V = IR

R = V/I = 220V/5A 44 Ω

Thus, the total resistance of the circuit is 440.

Now, we need to find out the number of 4840 bulbs should be connected in parallel to obtain a total resistance of 44. Suppose the number of 4840 bulbs required is x.

Then: 1/44 = 1/4840 × x

X = 4840/44 = 110

Thus, 110 bulbs can be connected in parallel in this circuit.

 

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