The current gain ($\beta$) in a common emitter configuration is defined as the ratio of change in collector current ($\Delta I_C$) to the change in base current ($\Delta I_B$) at a constant collector-emitter voltage.

Given: Change in base current, $\Delta I_B = 150 \text{ } \mu\text{A} - 100 \text{ } \mu\text{A} = 50 \text{ } \mu\text{A} = 50 \times 10^{-6} \text{ A}$ Change in collector current, $\Delta I_C = 10 \text{ mA} - 5 \text{ mA} = 5 \text{ mA} = 5 \times 10^{-3} \text{ A}$

Current gain, $\beta = \frac{\Delta I_C}{\Delta I_B}$ $\beta = \frac{5 \times 10^{-3} \text{ A}}{50 \times 10^{-6} \text{ A}} = \frac{5000 \times 10^{-6}}{50 \times 10^{-6}} = 100$

Therefore, the current gain is 100.