Q. 4 A3.8( 13 Votes )

Explain with the help of a labelled circuit diagram, how you will find the resistance of a combination of three resistors of resistances R1, R2 and R3 joined in parallel.

Answer :


Let the resistance of the three resistors be R1, R2 and R3, respectively. Let their combined resistance be R.


Let the total current flowing in the circuit be I and the strength of the battery be V. Then from Ohm's law, we have: V= IR------- (1)


We know that when the resistors are connected in parallel, the potential drop across each resistance is the same. Therefore:


I = I1+I2+I3


I = V/R1+ V/R2+ V/R3


1/R=1/R1+1/R2+ 1/R3


If two resistances are connected in parallel, then the resultant resistance will be


1/R=1/R1+1/R2+ 1/R3


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