1. **State the problem:** We need to find the magnitude of the electromotive force (emf) generated in a solenoid due to a changing current. 2. **Formula used:** The emf induced in a solenoid due to self-inductance is given by: $$|\varepsilon| = L \left| \frac{dI}{dt} \right|$$ where $L$ is the self-inductance and $\frac{dI}{dt}$ is the rate of change of current. 3. **Given values:** - Self-inductance, $L = 2$ H - Rate of change of current, $\frac{dI}{dt} = 0.1$ A/s 4. **Calculate the emf:** $$|\varepsilon| = 2 \times 0.1 = 0.2$$ 5. **Interpretation:** The magnitude of the emf generated to oppose the change in current is $0.2$ volts. This emf acts to oppose the increase or decrease in current according to Lenz's law.