If value of two resistance are 10 Ω and 20 Ω, and a current of 5A flow through circuit having p.d 12v, find value of third resistor if all 3 are connected in parallel.
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If value of two resistance are 10 Ω and 20 Ω, and a current of 5A flow through circuit having p.d 12v, find value of third resistor if all 3 are connected in parallel.
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Current = Potential difference / Equivalent Resistance
5 = 12/ Equivalent Resistance
Equivalent Resistance = 12/5 = 2.4 ohm
For parallel connection formula for Equivalent Resistance
1/R = 1/R1 + 1/R2 + 1/R3
R = 12/5
R1 = 10
R2 = 20
Putting values in formula,
5/12 = 1/10 + 1/20 +1/R3
1/R3 = 5/12 - 1/10 - 1/20
1/R3 = 4/15
R3 = 15/4 ohm = 3.75 ohm
So, third resistor is of 3.75 ohm
Thank you.