modified 9 years ago

Required help in resistance calculation

01:02:31

Required help in calculating resistance. When resistance around diode is just 6.62 ohms then how come resistance around diode and register of 1K ohm is 3.21k ohm and not 1006.62 ohm ?  Excuse me i am a beginner...

published 9 years ago

lmccoig

9 years ago

Example circuits may be better starting point when beginning. More voltage than ohm meter may be helpful. Ohm meter resistance values affect things as well. 1k ohm resistor is value of resistor. In series circuit same current flow through all components.

prady

9 years ago

Thanks Imccoig, but still understand if ohm meter's resistance affect circuit then how come resistance in the first circuit is just 6.62 ohms?

ferlop

9 years ago

It has to do with the fact that rectifier diodes are not resistors; Diode change resistance exponentially even when forward biased. The meter is going to maintain 1 volt output but by introducing a resistor in series you have changed the current flow, so you can not expect to have the same resistance as with the diode by itself. Analysis of the physics of a diode shows that the IV curve isn't a square-law but an exponential relationship of the general form: I{Vf}=Id(Exp{aVf}-1} Some one else might explain it better.

ferlop

9 years ago

Also change the value of the series resistor to 2k and to 10k and you will see the resistance of the diode increase exponentially.

wyoelk

9 years ago

Welcome hope you enjoy learning as we all are. Look at the Examples circuits. Use the search feature to look for circuits you might like. Have fun post,with questions, thats how we all learn. Maybe download the app "Lessons in Electricity" to help you learn more

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