Applications of Electromagnetic Induction
Simple Explanation
Electromagnetic induction powers generators (mechanical motion into electricity) and transformers (changing AC voltage between two coils, following Vs/Vp=Ns/Np) — two of the most important devices in all of electrical engineering.
Why Do We Need It?
Nearly all the world's electricity is generated by induction (in power plant generators) and its voltage is adjusted for safe, efficient transmission by transformers — both built entirely on the same underlying principle.
See It
A rectangular iron core with a primary coil of three loops wound on the left side and a secondary coil of three loops wound on the right side
Formula
The Transformer Equation
Vₛ/Vₚ = Nₛ/Nₚ
A transformer changes AC voltage between its primary and secondary coils in direct proportion to the ratio of their turns — more turns on one side means proportionally higher voltage on that side.
- Vₚ
- — voltage across the primary coil, in volts (V)
- Vₛ
- — voltage across the secondary coil, in volts (V)
- Nₚ
- — number of turns on the primary coil
- Nₛ
- — number of turns on the secondary coil
When to use it: Whenever a transformer's output (secondary) voltage needs to be found from its input voltage and the ratio of turns on its two coils.
Worked Example
Find a transformer's secondary voltage
A transformer has 1000 turns on its primary coil and 100 turns on its secondary coil, with 240 V applied to the primary. Find the secondary voltage.
Why Does This Work?
A changing current in the primary coil creates a changing flux in the shared iron core, which threads through the secondary coil too — inducing an EMF there by Faraday's law. Since the SAME changing flux links every turn on both coils, the induced EMF per turn is identical on each side, making the total voltage on each coil directly proportional to its own number of turns.
Real-Life Example
A phone charger's internal transformer
A phone charger converts 120 V or 230 V mains electricity down to just a few volts to safely charge a phone battery.
A small step-down transformer inside the charger uses far fewer turns on its secondary coil than its primary, reducing the voltage in direct proportion to the turns ratio.
Practice
A step-up transformer has 50 turns on its primary and 1000 turns on its secondary, with 12 V applied to the primary. Find the secondary voltage.
MediumCommon mistake
Assuming a transformer can also step up POWER, not just voltage — a transformer only changes the balance between voltage and current; it cannot create extra power (in fact real transformers always lose a small amount to heat).
Quick Review
- Vs/Vp = Ns/Np.
- More secondary turns than primary: step-up. Fewer: step-down.
- Generators convert motion to electricity; transformers change AC voltage — both use induction.