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Current Electricity

Question
CBSEENPH12039493

The current voltage relation of the diode is given by I = e(1000V/T-1) mA, where the applied voltage V is in volt and the temperature T is in kelvin. If a student makes an error measuring ± 0.01V while measuring the current of 5mA at 300K, what will be the error in the value of current in mA?

  • 0.2 mA

  • 0.02 mA

  • 05 mA

  • 0.05 mA

Solution

A.

0.2 mA

Given, I =(e1000V/T-1)mA
dv =±0.01 V 
T = 300 K
I = 5 mA
I = e1000V/T-1
I +1 = e1000V/T
Taking log on both sides, we get
log(l+T) = 1000V/T
On differentiating,
fraction numerator dl over denominator 1 plus 1 end fraction space equals space 1000 over straight T space dV
dl space equals space fraction numerator 1000 over denominator straight l plus straight T end fraction space equals space 1000 over straight T space dV
dl space equals space 1000 over straight T space straight x space left parenthesis straight l plus 1 right parenthesis space dV
rightwards double arrow space dl space equals space 1000 over 300 space straight x space left parenthesis 5 plus 1 right parenthesis space straight x 0.01 space equals space 0.2 space mA
So, error in the value of current is 0.2 mA 

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