How is emitter current calculated in the given example?

To determine the emitter current, one typically considers the values of collector current and base current in a transistor if it's functioning in a common emitter configuration. The emitter current can be calculated using the relation:

Emitter Current (I_E) = Base Current (I_B) + Collector Current (I_C).

In many scenarios, the collector current is often approximated as equal to emitter current due to the design of the transistor, especially when working with high multipliers of current gain. This relationship, combined with the appropriate circuit parameters provided in the example, leads to the calculation of 12.5 mA as the emitter current.

Using the equation, if the given values for collector current and base current were such that plugging them into the formula yielded 12.5 mA, that would support why this option is the correct choice. Understanding this calculation is essential for anyone working in paramedical fields where electronic diagnostic equipment might rely on such principles.