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Parallel Resistor Formula

The resistor (R) is a substance which has the property of opposing the flow of an electric current through it. The SI unit of resistance is ohm and its unit symbol is represented by Ω. 


Resistor obeys the ohm’s law. Ohm’s law states that the ratio of potential difference (V) between any two points on a conductor to the current (I) through them is constant, provided temperature of the conductor remains constant. 

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 Formula - Resistor:Equivalent Circuit – Resistor:R = V / IThe current I is flow through resistor as shown in the equivalent circuit. Let us see the equivalent circuit of resistor that be connected in series and parallel.Example Problem:1. Find the value of resistor, when current of 4A is flow through the circuit and supply voltage is 24 V.Solution:Formula - R = V / IR = 24 / 4 = 6ΩAnswer: R = 6Ω



Parallel Resistor Formula: 

 Parallel Resistor: 


The resistor which are connected in parallel means positive charge of one resistor is connected to the positive charge of other resistor as like as negative charge of resistor. It is called parallel resistor. Let us see the equivalent circuit and formula to be used for the equivalent resistor. 

 Equivalent Circuit of Resistor – Parallel Combination:In this equivalent circuit, the resistor is connected parallel to the supply.Formula for the equivalent resistor in the circuit is 1 / R = (1 / R1) + (1 / R2) + (1 / R3) + ….(1 / Rn) 


 Example Problem – Equivalent Circuit of parallel combination:2. What is the equivalent resistor of the above circuit whose R1 = 7Ω, R2 = 6Ω and R3 = 5Ω and also find its voltage value by passing oc current is 1.5 Amp.Solution:Formula: 1 / R = (1 / R1) + (1 / R2) + (1 / R3)1 / R = (1 / 7) + (1 / 6) + (1 / 5) = 18/210R = 210 / 18 = 11.66ΩR = 11.66ΩTo find Voltage supply of circuit:Formula: V = IRV = 1.5 (11.66) = 17.49 voltsAnswer: Voltage = 17.49 V

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