Question

How does a magnetic core transformer work?

Answer 1

A magnetic core transformer works by transferring electrical energy from one circuit to another using electromagnetic induction. Here’s a simple breakdown of how it works:

1. Basic Components of a Transformer:

   - Primary Coil (Winding): The coil where the input voltage is applied.
   - Secondary Coil (Winding): The coil where the output voltage is taken.
   - Magnetic Core: The central part of the transformer, usually made of a ferromagnetic material (like iron), which helps guide the magnetic field from the primary coil to the secondary coil.

2. How It Works:

   - Input Power: When alternating current (AC) flows through the primary coil, it creates a changing magnetic field around it. This happens because AC changes direction periodically, causing the magnetic field to expand and contract.
   
   - Magnetic Flux: The changing magnetic field (or flux) is passed through the magnetic core. The core acts like a guide, directing the magnetic flux to the secondary coil.

   - Induced Voltage: When the changing magnetic field reaches the secondary coil, it induces an alternating voltage across the secondary coil. This happens due to electromagnetic induction — a principle discovered by Michael Faraday. The rate of change in the magnetic field within the core induces a voltage in the secondary coil.

   - Output Power: The voltage in the secondary coil is proportional to the turns ratio (the number of turns of wire in the primary coil to the number of turns in the secondary coil). If the secondary coil has more turns than the primary, the output voltage is higher (a step-up transformer). If the secondary coil has fewer turns, the output voltage is lower (a step-down transformer).

3. Key Points:

   - AC is used because the magnetic field needs to change over time to induce voltage in the secondary coil.
   - Magnetic Core is crucial because it enhances the efficiency of the transformer by providing a low-resistance path for the magnetic flux.
   - Turns Ratio: Determines whether the transformer will increase or decrease the voltage. The formula is:
     \[
     \frac{V_{\text{primary}}}{V_{\text{secondary}}} = \frac{N_{\text{primary}}}{N_{\text{secondary}}}
     \]
     Where \(V\) is the voltage and \(N\) is the number of turns in the coil.

Example:

1. If you have a transformer with 100 turns on the primary coil and 50 turns on the secondary coil, and you apply 120V to the primary, the voltage in the secondary coil will be:
   

  \[
  V_{\text{secondary}} = \frac{50}{100} \times 120V = 60V
  \]
  This means the transformer steps down the voltage from 120V to 60V.

In summary, a magnetic core transformer uses electromagnetic induction to transfer energy between two coils, adjusting the voltage based on the number of turns in each coil. The magnetic core helps direct and enhance the magnetic field, making the process more efficient.