Electric heaters designed to be used on a 220 V electric supply line are rated as 11W. If the maximum supply current is 5A, how many electric heaters can be connected in parallel with each other across 220V supply line? How much total energy is consumed by these in 20 minutes?
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Step-by-step explanation:
let there be n no of resisitors in parallel with equal resistance
1/R = 1/r + 1/r +......+n/r
=)1/R= n/r
=) R = r/n .....(1)
WE KNOW THAT POWER (P) = V²/r
( we take this equation because in parallel voltage is same)
=)r= V²/P=(220 × 220)/11= 4400 ohm
by ohms law ,
I= V/ R = 220 × n/4400 =) 5 = n/20
=) n = 100 resistors
each power = 11W
as voltage is same
E = V²t ( 1/r + 1/r +....+100 times)
= 220 × 220× (100/r)× 20/60
= 220 × 220 × 100/4400 × 1/3
= 366.67 kW h
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