Correct Option: (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Step 1 (Foundational Principle): [0.25 Mark]
An ideal transformer is defined as one where there is no dissipation of energy due to resistance of windings, hysteresis, or eddy currents. The governing principle for an ideal transformer is the Law of Conservation of Energy, which states that the input power equals the output power:
$$P_{in} = P_{out} \implies V_p I_p = V_s I_s$$Step 2 (Analysis of Assertion and Reason): [0.50 Mark]
- Assertion (A): In an ideal transformer, by definition, there are no energy losses (efficiency $\eta = 100\%$). Thus, the statement is True.
- Reason (R): For a step-down transformer, the turns ratio $N_s < N_p$, which implies $V_s < V_p$. Since $V_p I_p = V_s I_s$, it follows that $I_s > I_p$. Thus, the statement is True.
Step 3 (Final Conclusion): [0.25 Mark]
While both statements are scientifically accurate, the Reason (R) explains the transformation mechanism of voltage and current, whereas the Assertion (A) refers to the efficiency/energy conservation of the device. Therefore, (R) is not the correct explanation for (A).
💡 EL10 Concept Insight: Think of a transformer like a trade-off: if you want to lower the "pressure" (voltage) of electricity, the "flow" (current) must speed up to keep the total amount of power exactly the same, just like how a wide river flows slower than a narrow one to carry the same amount of water.