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Question:

How many 176 Ω resistors (in parallel) are required to carry 5A on a 220V line?

Solution:

Step 1 : Equivalent resistanceLetnbe the number of resistors to be connected in parallelThen,R1=R2=..=Rn=R=176 ΩNow,1Req=1R1+1R2+.1Rn⇒1Req=nR1=n176⇒Req=176/n(1)Step 2 : Applying Ohm's lawV=IReq⇒220=5Req⇒220=5×176/n(Using Equation(1))⇒n=4Hence, four resistors are required.