Discussion of Ohm’s Law

Introduction

            This page shows dynamically how the current flow and brightness of a light bulb changes as the rheostat brush position is changed.

 

Math for Ohm’s Law

RR

 

V=

 

RL

 

RV 300 Ohms
 

The resistance, RR, to the right of the arrow (brush) on the variable 300 Ohm resistor is in series with the other two resistances, the light bulb which is RB=150 Ohms and the part of the variable resistor to the left of the brush, RL, which are in parallel.  The law for addition of resistances in parallel is:

                                                            

The total resistance of the circuit is then:

                                                      

The corresponding current is then the Voltage, V, divided by RTotal