Which parameter determines whether a transformer is classified as step-up or step-down?

• A. The ratio of the number of turns in the secondary coil to the number of turns in the primary coil, $\frac{N_s}{N_p}$
• B. The frequency of the alternating current supplied to the transformer
• C. The total resistance of the transformer windings
• D. The core material used in the transformer

Answer: (A)

Verified step by step guidance

1. Understand that a transformer changes voltage levels based on the relationship between its primary and secondary coils.
2. Recall that the key parameter in a transformer is the number of turns of wire in each coil: the primary coil (N_p) and the secondary coil (N_s).
3. Recognize that the voltage ratio between the secondary and primary sides is directly proportional to the turns ratio, given by the formula: \(\frac{V_s}{V_p} = \frac{N_s}{N_p}\).
4. Identify that if \(\frac{N_s}{N_p} > 1\), the transformer increases voltage (step-up), and if \(\frac{N_s}{N_p} < 1\), it decreases voltage (step-down).
5. Conclude that the parameter determining whether a transformer is step-up or step-down is the ratio of the number of turns in the secondary coil to the number of turns in the primary coil, \(\frac{N_s}{N_p}\).