Question

you are given several identical resistors each having resistance of 10 ohms and a max current of 1A is allowed to pass through each resistor. it is required to make a suitable combination of these resistances of 5 Ohms which can carry a current of 4A. find the number of such resistances that will be required

Answer 1

Dear Student ,
P = RI² = 10*1 = 10 watt each resistor
P² = R²I⁴= 5*4² = 5*16 = 80 watt
n = P²/P = 80/10 = 8 pieces....infact :
4 amps require 4 parallels : 10//10//10//10 = 10/4 = 2.5 ohm
5 ohms requires 2 series of 2.5 ohm , hence 4*2 = 8 resistors

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