The transistor has a collector current of 10 mA and a base current of 40 mA. What is the current gain of the transistor? A. 250 µA B. 350 µA C. 0.25 µA D. 300 µA E. None of the above

The correct

The current gain of a transistor is the ratio of the collector current to the base current. It is typically denoted by the Greek letter $\beta$ (beta). In this case, the current gain is $\beta = \frac{I_C}{I_B} = \frac{10\text{ mA}}{40\text{ mA}} = 0.25$.

Option A is incorrect because it is the base current, not the current gain. Option C is incorrect because it is the current gain divided by 1000. Option D is incorrect because it is the collector current. Option E is incorrect because it is not one of the possible answers.