• Transformers are devices that step up or step down voltage using the principle of electromagnetic induction.
  • Step-up Transformers: Increase voltage.
  • Step-down Transformers: Decrease voltage.

Efficiency: Power input equals power output, but transformers are never 100% efficient due to losses (e.g., resistance, leakage flux, core losses).

POWER LOSSES IN TRANSMISSION

• Power is lost in transmission lines due to resistance and leakage. These losses can be minimized by transmitting power at high voltage and low current.

Transformers work based on the principle of electromagnetic induction, transferring electrical energy between two or more coils of wire without direct electrical contact. The two main types of transformers are:

1. Step-Up Transformer

• Purpose: Increases voltage from the primary to the secondary coil.
• How It Works:
  • A low voltage is applied to the primary coil, which is connected to an alternating current (AC) supply.
  • The alternating current in the primary coil generates a changing magnetic field around the coil.
  • This changing magnetic field induces an electromotive force (EMF) in the secondary coil, which has more turns of wire than the primary coil.
  • Because the secondary coil has more turns, it produces a higher voltage than what was initially applied to the primary coil.
  • The increase in voltage follows the formula: VsVp=NsNp​​ where Vs​ and Vp​ are the voltages in the secondary and primary coils, and Ns​ and Np are the number of turns in the secondary and primary coils, respectively.

2. Step-Down Transformer

• Purpose: Decreases voltage from the primary to the secondary coil.
• How It Works:
  • A high voltage is applied to the primary coil, connected to an AC supply.
  • Like in the step-up transformer, the alternating current generates a changing magnetic field around the primary coil.
  • This magnetic field induces an EMF in the secondary coil, which has fewer turns of wire than the primary coil.
  • The secondary coil thus produces a lower voltage.
  • The voltage decrease follows the same formula: ………………….​, so the voltage in the secondary coil is lower than in the primary.

Key Differences

• Step-Up Transformer: More turns in the secondary coil than in the primary, increasing the voltage.
• Step-Down Transformer: Fewer turns in the secondary coil than in the primary, decreasing the voltage.

In both cases, transformers operate only with alternating current (AC) since direct current (DC) does not produce the changing magnetic field required for induction.