Question

In space charge limited region, the plate current in a diode is $10\, mA$ for plate voltage $150\, V$. If the plate voltagte is increased to $600\,V$, then the plate current will be

• A. 10 mA
• B. 40 mA
• C. 80 mA
• D. 160 mA

Answer 1

Answer: (C)

In space charge limited region, the plate current is given by Child's law $i_{p}=K V_{p}^{3 / 2}$
Thus, $\frac{i_{p_{2}}}{i_{p_{1}}}=\left(\frac{V_{p_{2}}}{V_{p_{1}}}\right)^{3 / 2}=\left(\frac{600}{150}\right)^{3 / 2}$
$=(4)^{3 / 2}=8$
or $i_{p_{2}}=i_{p_{1}} \times 8=10 \times 8\, mA =80\, mA$