Ideal transformer relationships — current calculation: A power transformer steps 100 V down to 10 V. If the primary current is 2 A, determine the secondary current (assume an ideal transformer).

Introduction / Context:
Transformers trade voltage for current while conserving power (minus losses). Understanding the inverse relationship between voltage ratio and current ratio is essential for sizing conductors, fuses, and loads in power electronics and distribution.

Given Data / Assumptions:

• Primary voltage V_p = 100 V.
• Secondary voltage V_s = 10 V.
• Primary current I_p = 2 A.
• Assume ideal transformer: P_in = P_out → V_p * I_p = V_s * I_s.

Concept / Approach:
For an ideal transformer, the current ratio is inverse of the voltage ratio: I_s / I_p = V_p / V_s. Use this to find I_s directly without needing turns counts explicitly. This reflects power conservation and magnetic coupling in the core.

Step-by-Step Solution:
Compute voltage ratio: V_p / V_s = 100 / 10 = 10.Relate currents: I_s = I_p * (V_p / V_s).Insert values: I_s = 2 A * 10 = 20 A.Therefore, the secondary current is 20 A (ideal case).

Verification / Alternative check:
Power check: P_in = 100 V * 2 A = 200 W. P_out = 10 V * 20 A = 200 W. Powers match, validating the calculation.

Why Other Options Are Wrong:
(a) 50 A overstates the inverse ratio. (b) 12 A misapplies ratios. (c) 5 A incorrectly uses a direct rather than inverse relationship. (e) Not applicable because 20 A is correct.

Common Pitfalls:
Forgetting the inverse relationship, or applying real-world efficiency (less than 100%) to an idealized question. Even with small losses, the result would remain close to 20 A.

Final Answer:
20 A.