Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Parallel Connection of Resistors

Introduction

When two resistors \(R_1\) and \(R_2\) are connected in parallel, effective resistance of the circuit becomes \(R_e=R_1R_2/(R_1+R_2)\).

Apparatus

Voltmeter, Ammeter, Power Supply, Resistors and Connecting Wires

Procedure

raa.png

Connect three resistors (\(R_1\), \(R_2\) and \(R_3\)), an ammeter, a cell and a plug key, as shown in figure. Close the key and note the ammeter reading. This gives the current \(i\) in the circuit. Now, connect the ammeter in the branch of the circuit that has \(R_1\) and note the reading. This gives the current \(i_1\) through the branch. Similarly, place the ammeter in the branches containing \(R_2\) and \(R_3\), and measure the current \(i_2\) and \(i_3\) respectively. You will find that the current \(i\) gets divided into the branches such that \(i=i_1+i_2+i_3\).