1.

Two bulbs of 220 V and 100 W are firs connected in series and then in parallel with a supply of 220 V. Total power in buth the cases will be ........

Answer»

50 W, 100 W
100 W, 50 W
200 W, 150 W
50 W, 200 W

SOLUTION :50 W, 200 W
Power in series combination of resistances
`P_(s)= (P_(1) xx P_(2))/(P_(1) + P_(2))`
but `P_(1)= P_(2)`
= 100W
`THEREFORE P_(S) = (100 xx 100)/(100 + 100)`
50 W
Power in parallel combination,
`P_(p) = P_(1) + p_(2)`
but `P_(1) = P_(2) `
= 100 W
`P_(p) = 100 + 100 `
= 200 W


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