Lesson Notes By Weeks and Term v4 - SHS 3

Lesson Video

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Performance objectives

• Describe the relationship between voltage and current in a transformer.
• Discuss the factors that affect transformer performance and efficiency.
• Describe how energy losses in a transformer can be minimised.
• Identify real-life applications of transformers in Ghana.

Lesson summary

Every day, we use electricity supplied by the Electricity Company of Ghana (ECG). This power travels hundreds of kilometres from dams like Akosombo or thermal plants in Tema to our homes, schools, and businesses. How does this electricity travel so far without losing most of its energy? The answer lies in a simple but brilliant device called the transformer. You see them everywhere – in the big cages at GRIDCo substations, on the poles in your neighbourhood, and even inside your phone charger. This lesson explores how transformers work, why they are not perfectly efficient, and how engineers make them better.

Lesson notes

2.1. What is a Transformer and How Does it Work?

A transformer is a static electrical device that transfers electrical energy from one AC circuit to another at the same frequency, but with a different voltage and current level. Principle: It works on the principle of mutual electromagnetic induction. An alternating current (AC) flows through the primary coil. This creates a continuously changing magnetic field in the soft iron core. The soft iron core concentrates this changing magnetic flux and links it to the secondary coil. According to Faraday's Law of Induction, this changing magnetic flux induces an alternating electromotive force (e.m.f.), or voltage, in the secondary coil.

Crucial Point: Transformers ONLY work with Alternating Current (AC). A direct current (DC) creates a steady magnetic field, which does not change and therefore cannot induce a voltage in the secondary coil. 2.2. The Ideal Transformer

An ideal transformer is a theoretical model that is 100% efficient. This means there are no energy losses. In an ideal transformer: *Power Input = Power Output* *P p = P s * *V p I p = V s I s *

Evaluation guide

• Discuss the factors that affect the transmission of power and efficiency of a
• transformer and w ays of improving its efficiency.
• Talk for learning:
•  Describe the effect of transformers on the relationship between the potential difference