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 R_{1}, R_{2} and R_{3} joined in parallel.

Answer :

Let the resistance of the three resistors be R_{1}, R_{2} and R_{3}, 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 = I_{1}+I_{2}+I_{3}

I = V/R_{1}+ V/R_{2}+ V/R_{3}

1/R=1/R_{1}+1/R_{2}+ 1/R_{3}

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

1/R=1/R_{1}+1/R_{2}+ 1/R_{3}

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