An ideal transformer has primary-to-secondary turns ratio 100:5. Find secondary voltage for a 190 V AC primary.

Solution & explanation

1. Given: Nₚ = 100; Nₛ = 5; Vₚ = 190 V.

2. For an ideal transformer supplied with AC, voltage ratio equals turns ratio.

   $$\frac{V_s}{V_p}=\frac{N_s}{N_p}$$

3. Multiply both sides by the primary voltage.

   $$V_s=\frac{N_s\times V_p}{N_p}$$

4. Insert the given values.

   $$V_s=\frac{950}{100}$$

5. Multiply first, then divide.

   $$V_s=\frac{950}{100}=9.5$$

6. This is a step-down transformer because the secondary has fewer turns.

7. State the result with units: Vₛ = 9.5 V.

Vₛ = 9.5 V