several electric bulbs are designed to use 220 volt electric supply,are rated 10w.How many lamps can

Asked by  | 10th Aug, 2009, 01:55: PM

Expert Answer:

Here  V = 220 V

          P = 10 W

          I = 5A

Resistance of each lamp R = V2 / P =(220 x220) /10

                                                R = 4840 ohm

Now, let n number of lamps be connected in parallel of resistance R each

So equivalnt resistance = R' = R/n = (4840/n)ohm

Using V = IR' , we get

220 = ( 5 x 4840) / n

or n = ( 5 x 4840) / 220

      n = 10

Thus 10 lamps can be connected in parallel with each other across the two wires of 220 volt if the maximum allowance of current is 5 A.

Answered by  | 10th Aug, 2009, 02:01: PM

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