In this lecture, we study one of the most important applications of mutual induction — the Transformer. We understand what transformers are, their working principle, and their main types.

⚡ What is a Transformer?

A transformer is an electrical device used to:

• Increase (step up) voltage

• Decrease (step down) voltage

It works only with alternating current (AC).

Transformers are essential in:

• Power transmission systems

• Electricity grids

• Electronic devices and adapters

🔄 Working Principle of Transformer

A transformer works on the principle of Mutual Induction.

When alternating current flows in the primary coil, it produces a changing magnetic flux, which induces EMF in the secondary coil.

🔹 Basic Parts:

• Primary coil

• Secondary coil

• Soft iron core

📐 Transformer Formula

VsVp=NsNp\frac{V_s}{V_p} = \frac{N_s}{N_p}Vp​Vs​​=Np​Ns​​

where:

• VsV_sVs​ = secondary voltage

• VpV_pVp​ = primary voltage

• NsN_sNs​ = number of turns in secondary

• NpN_pNp​ = number of turns in primary

Also,

VpIp=VsIsV_p I_p = V_s I_sVp​Ip​=Vs​Is​

(For ideal transformer — power remains constant)

🔌 Main Types of Transformers

1️⃣ Step-Up Transformer

• Increases voltage

• Ns>NpN_s > N_pNs​>Np​

• Used in power stations for transmission

2️⃣ Step-Down Transformer

• Decreases voltage

• Ns<NpN_s < N_pNs​<Np​

• Used in homes and electronic devices

3️⃣ Isolation Transformer

• Ns=NpN_s = N_pNs​=Np​

• Voltage remains same

• Used for safety purposes

📌 Why Transformers Are Important

• Reduce energy loss in transmission

• Make electricity distribution efficient

• Protect electrical devices

🎯 By the End of This Lecture

You will:

• Define a transformer

• Explain its working principle

• Derive transformer voltage relation

• Differentiate between step-up and step-down transformers

This lecture completes the major practical applications of electromagnetic induction and connects physics with real-world power systems.