Question

how many 440 ohm resistance in parallel are required to carry 5 ampere current into 20 volt line

Answer 1

You need 5A current over 220V voltage difference. So the total resistance of the circuit in between would be R=V/I, here R=220V/5A=44 Ohm .Now, you have only 440Ohm resistors which are to be connected in parallel only. Let 'n' is the number of 440 Ohm resistors connected in parallel to achieve overall 44 Ohm resistance.Using the formula of equivalent resistance for resistors connected in parallel we get n/440 = 1/44 [(1/R)=(1/R1)+(1/R2)+.... ; R is equivalent resistance, Ri is the resistance of i-th resistor in parallel]So clearly n=10You need ten(10) 440 Ohm resistors in parallel in order to get total 5A current in 220V voltage difference