Parallel Circuits Lecture 4 PDF

IM 115 Parallel Circuits What is a Parallel Circuit?  When two or more resistors are individually connected between the same two points, they are in parallel with each other. A parallel circuit provides more than one path for current What is a Parallel Circuit?  When there is more than on...

IM 115 Parallel Circuits What is a Parallel Circuit?  When two or more resistors are individually connected between the same two points, they are in parallel with each other. A parallel circuit provides more than one path for current What is a Parallel Circuit?  When there is more than one path for the current to flow around a circuit and back to where it started -- then you have a parallel circuit  Eachof the parallel paths is called a “branch” Identifying Parallel Circuits Identifying Parallel Circuits Identifying Parallel Circuits R2 R1 R2 R1 Voltage Drops in Parallel Circuits  When we have a parallel circuit, the voltage drop will be the same across all the branches of a parallel circuit  VS = V1 = V2 = V3 R1 V1 R2 V2 R3 V3 Parallel Resistance  How does the number of current paths affect the circuit characteristics?  Ifwe have more than one path for the current to move through, it will not affect the current in other branches as the voltage across these branches will remain the same Parallel Resistance Parallel Resistance Parallel Resistance Parallel Resistance  Formula for two resistors in parallel IT I1 I2 VS R1 R2 Parallel Resistance  Start with the current node rule: I T  I1  I 2 Vs VS VS   RT R1 R2 1 1 1   RT R1 R2 Parallel Resistance  Formula for two resistors in parallel 1 RT  1  1 R1 R2 Parallel Resistance  Formula for two resistors in parallel R1 R2 RT  R1  R2 Parallel Resistance  Formula for multiple resistors in parallel IT I1 I2 I3 VS R1 R2 R3 Parallel Resistance  Formula for multiple resistors in parallel 1 RT  1  1  1 .... R1 R2 R3 Find the Total Resistance Find the Total Resistance Find the Total Resistance Ohm’s Law  Christmas tree lights are usually connected in parallel. If a set of lights is connected to a 120 V source and the filament of each bulb has a resistance of 2 k, what is the current through each bulb? What is the total current if there is 50 bulbs? Why is it better to have these bulbs in parallel rather than in series? Ohm’s Law If voltage  120 V and resistance is 2 k for each filament - then Ohm' s Law says current must be : V 120 V I  .060 A  60.0 mA R 2 k 50 bulbs x 60 mA  3000 mA  3.0 A Applications  Automotive lights with - brake lights, tail lights, headlights, and high beams  House wiring  Range burner switch with three resistors to select current to burner