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If each diode in Fig. 14.13 has a forward bias resistance  25\Omega and infinite resistance in reverse bias, what will be the values of the current I1, I2, I3, and I4?

Answers (1)

Explanation:-

According to the problem forward biases resistance = 25 \Omega and reverse biases resistance=\infty

As shown in figure,e the diode in branch CD is in reverse biases which have infinite resistance

So, the current in that branch is zero i.e I_{3}=\theta

Resistance in branch AB=25+125=150\Omega\ say \ R_{1}

Resistance in branch EF=25+125=150\Omega say R_{2}

AB is parallel to EF, So effective resistance

\frac{1}{R'}=\frac{1}{R_{1}}+\frac{1}{R_{2}}=\frac{1}{150}+\frac{1}{150}=\frac{2}{150}\\\Rightarrow R'=75\Omega

Total resistance R of the circuit=R'=25=75+25=100\Omega

current

I_{1}=\frac{V}{R}=\frac{5}{100}=0.05A

According to Kirchhoff's, current law (KCL)

I_{1}=I_{4}+I_{2}+I_{3}\: \: \: \: \: \: \: \left ( I_{3}=0 \right )\\ SoI_{1}=I_{4}+I_{2}

Here the resistances R1 and R2 are the same

i.e

  I_{4}=I_{2}\\ \therefore I_{1}=2I_{2}\\ \Rightarrow I_{2}=\frac{I_{1}}{2}=\frac{0.05}{2}=0.025A

And I4 =0.025A

Therefore we get I1 =0.05A,I2 =0.025A,I3 =0 and I4 =0.025A

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