Primary Impedance (ZP) vs. Secondary Load Impedance (ZS) in a Step-Up Transformer

In a step-up transformer, the primary winding has fewer turns than the secondary winding. This results in an increase in voltage from the primary side to the secondary side. The relationship between the primary and secondary voltages is determined by the turns ratio of the transformer.

The impedance of a transformer refers to the opposition to the flow of electric current. It is measured in ohms and is composed of two components: resistance and reactance. The primary and secondary windings of a transformer have their own impedance.

The given question states that the secondary load impedance of the transformer is ZS. It asks us to determine the relationship between the primary impedance (ZP) and the secondary load impedance (ZS).

To understand this relationship, let's consider the key factors:

1. Turns Ratio:
The turns ratio of a transformer is defined as the ratio of the number of turns in the secondary winding (Ns) to the number of turns in the primary winding (Np). It is denoted by "a" and is given by a = Ns/Np.

2. Voltage Ratio:
The voltage ratio of a transformer is equal to the turns ratio. It represents the ratio of the secondary voltage (Vs) to the primary voltage (Vp). It is given by Vs/Vp = a.

Now, let's analyze the relationship between ZP and ZS:

- If the secondary load impedance (ZS) is greater than the primary impedance (ZP), it means that the secondary current (Is) is greater than the primary current (Ip).
- According to Ohm's law, V = I * Z, where V is the voltage, I is the current, and Z is the impedance.
- Since the voltage ratio (Vs/Vp) is equal to the turns ratio (a), and the voltage is directly proportional to the current in a transformer, it follows that Is/Ip = a.
- Therefore, if Is > Ip, it implies that a > 1 (since a = Ns/Np).
- As a result, the primary impedance (ZP) will be less than the secondary load impedance (ZS) because the current on the primary side is smaller than the current on the secondary side.

Hence, the correct answer is option 'C': The primary impedance (ZP) will be less than the secondary load impedance (ZS).