The correct relation for α, βfor a transistor :

The correct relation for $\alpha$, $\beta$ for a transistor :
A $\beta = \dfrac{1 - \alpha}{\alpha}$
B $\beta = \dfrac{\alpha}{1 - \alpha}$
C $\alpha = \dfrac{\beta - 1}{\beta}$
D $\alpha\beta = 1$

Detailed Solution

$\alpha = \dfrac{I_C}{I_E}$ and $\beta = \dfrac{I_C}{I_B}$, with $I_E = I_B + I_C$.
$\beta = \dfrac{I_C}{I_E - I_C} = \dfrac{I_C/I_E}{1 - I_C/I_E}$
$\beta = \dfrac{\alpha}{1 - \alpha}$
(Equivalently $\alpha = \dfrac{\beta}{1 + \beta}$.)

Transistor Current Gains in past papers

3 questions from this chapter have appeared across 3 exam years.

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Practise Transistor Current Gains All 3 questions This chapter in 2000 AIPMT