In an ideal 1:8 step down transformer, the primary power is 10 kW and the second current is 25 A. The primary voltage is:

Explanation

In a transformer, the power in the primary side equals the power in the secondary side (ignoring losses). The relationship between the voltages and currents is given by the equation: Vp / Vs = Np / Ns = Is / Ip, where V is voltage, I is current, and N is the number of turns in the primary and secondary coils.Given that it's a 1:8 step-down transformer, the secondary current is 25 A, and the primary power is 10 kW. First, we find the secondary voltage using the power equation: P = V * I, thus Vs = P / Is = 10,000 W / 25 A = 400 V. Now, using the transformer ratio (1:8), we find the primary voltage: Vp = Vs * 8 = 400 V * 8 = 3200 V.Option A (25,600V) is incorrect as it greatly exceeds the calculated primary voltage. Option C (400V) is the secondary voltage, not the primary. Option D (50V) is not a feasible voltage given the power and transformer specifications.