Lesson Notes By Weeks and Term v4 - SHS 3

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Describe how transformers change voltage and current.
• Discuss the factors that affect transformer performance.
• Explain how to improve transformer efficiency.
• Apply formulas to calculate voltage and efficiency.

Lesson summary

Welcome, future engineers and scientists! Today, we are exploring a device that is absolutely essential to our modern lives in Ghana: the transformer. From the massive transformers at the Akosombo Dam and GRIDCo substations that send power across the country, to the small block in your phone charger that powers your device safely, transformers are everywhere. Understanding how they work, why they lose energy, and how we can make them better is crucial for building a more energy-efficient nation. This lesson will demystify the transformer and connect complex physics principles to the electricity you use every day.

Lesson notes

A. The Ideal Transformer: A Quick Recap

A transformer works on the principle of mutual electromagnetic induction. It consists of two coils, a primary coil and a secondary coil, wound on a common laminated soft iron core. When an alternating current (AC) flows through the primary coil, it creates a continuously changing magnetic field in the core. This changing magnetic flux links with the secondary coil. According to Faraday's Law of Induction, this induces an alternating electromotive force (e.m.f.) or voltage across the secondary coil.

For an ideal transformer (one that is 100% efficient, with no energy loss), two key relationships hold true: The Transformer Equation: The ratio of the secondary voltage (`Vs`) to the primary voltage (`Vp`) is equal to the ratio of the number of turns in the secondary coil (`Ns`) to the number of turns in the primary coil (`Np`).

`Vs / Vp = Ns / Np` Step-up Transformer: `Ns > Np`, so `Vs > Vp`. Voltage is increased. Step-down Transformer: `Ns < Np`, so `Vs < Vp`. Voltage is decreased. Conservation of Power: In an ideal transformer, power input equals power output. `Power_in = Power_out` `Vp * Ip = Vs * Is`

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