### Correct Option: D. The secondary voltage is less than the primary voltage. ### Detailed Explanation: A step-down transformer is a device used to convert a higher voltage in the primary coil to a lower voltage in the secondary coil. This is achieved through the principle of electromagnetic induction, which is governed by Faraday's law of electromagnetic induction. #### How a Step-Down Transformer Works: 1. **Basic Structure**: A transformer consists of two coils of wire, known as the primary coil and the secondary coil, wound around a magnetic core. The primary coil is connected to an AC voltage source, while the secondary coil is connected to the load. 2. **Induction Process**: When an alternating current flows through the primary coil, it creates a changing magnetic field around it. This changing magnetic field induces a voltage in the secondary coil due to electromagnetic induction. 3. **Turn Ratio**: The relationship between the primary voltage (V₁) and the secondary voltage (V₂) is determined by the ratio of the number of turns in the primary coil (N₁) to the number of turns in the secondary coil (N₂). This relationship is given by the formula: \[ \frac{V₁}{V₂} = \frac{N₁}{N₂} \] For a step-down transformer, the number of turns in the secondary coil (N₂) is less than the number of turns in the primary coil (N₁), which means: \[ N₂ < N₁ \implies V₂ < V₁ \] Therefore, the secondary voltage (V₂) is less than the primary voltage (V₁). #### Why Option D is Correct: - Since in a step-down transformer, the secondary coil has fewer turns than the primary coil, the voltage induced in the secondary coil is lower than that in the primary coil. This directly supports option D: "The secondary voltage is less than the primary voltage." ### Why the Other Options are Incorrect: - **Option A: The secondary voltage is greater than the primary voltage.** - This statement is false because, in a step-down transformer, the primary voltage is always greater than the secondary voltage. The purpose of a step-down transformer is to reduce voltage, not increase it. - **Option B: The number of turns in the secondary coil is greater than the number of turns in the primary coil.** - This statement is also incorrect. In a step-down transformer, the secondary coil has fewer turns than the primary coil. If the secondary coil had more turns, it would be a step-up transformer, which increases voltage. - **Option C: The primary coil is designed to draw less current than the secondary coil.** - This statement is misleading. In a step-down transformer, while the secondary voltage is lower, the current in the secondary coil is higher than in the primary coil due to the conservation of energy (ignoring losses). The relationship is given by: \[ P₁ = P₂ \implies V₁I₁ = V₂I₂ \] Since \(V₂ < V₁\), it follows that \(I₂ > I₁\). Therefore, the primary coil draws less current than the secondary coil, making this statement incorrect. ### Summary: - A step-down transformer reduces voltage from primary to secondary. - The secondary voltage is always less than the primary voltage (Option D). - The number of turns in the secondary coil is less than in the primary coil. - The current in the secondary coil is greater than in the primary coil due to energy conservation. ### Revision Summary: - Step-down transformers reduce voltage (V₂ < V₁). - The number of turns in the secondary coil is less than in the primary coil (N₂ < N₁). - Current in the secondary coil is greater than in the primary coil (I₂ > I₁). - The relationship between voltage and turns is given by \( \frac{V₁}{V₂} = \frac{N₁}{N₂} \).