Transformer
Also known as: step-up transformer, step-down transformer
Grade 9-12
View on concept mapA device that changes AC voltage using electromagnetic induction between two coils on a shared iron core. Transformers make the entire electrical grid possible.
Definition
A device that changes AC voltage using electromagnetic induction between two coils on a shared iron core.
💡 Intuition
A transformer trades voltage for current (or vice versa) — like a gear system trades speed for torque.
🎯 Core Idea
Transformers only work with AC — the changing current in the primary coil creates a changing magnetic flux that induces voltage in the secondary.
Example
Formula
Notation
V_p and V_s are the primary and secondary voltages in volts, N_p and N_s are the number of turns, I_p and I_s are the primary and secondary currents in amperes, and \Phi is the magnetic flux in webers (Wb).
🌟 Why It Matters
Transformers make the entire electrical grid possible. Power stations step voltage up to 500,000 V for long-distance transmission (reducing current and I^2R heat losses by a factor of thousands), then substations step it back down for homes and businesses. Without transformers, electricity could only travel short distances efficiently.
💭 Hint When Stuck
When solving a transformer problem, first identify the primary and secondary coils and their turn counts N_p and N_s. Then use the turns ratio V_s/V_p = N_s/N_p to find the unknown voltage. If asked about current, apply power conservation: V_p I_p = V_s I_s (assuming an ideal transformer).
Formal View
Related Concepts
🚧 Common Stuck Point
A transformer doesn't create energy — if voltage goes up, current goes down proportionally (power is conserved).
⚠️ Common Mistakes
- Trying to use a transformer with direct current (DC) — transformers only work with alternating current because they rely on a changing magnetic flux.
- Forgetting that power is conserved: if the secondary voltage is higher, the secondary current must be lower, not the same.
- Mixing up primary and secondary — the primary coil is connected to the input (source), the secondary to the output (load).
Go Deeper
Frequently Asked Questions
What is Transformer in Physics?
A device that changes AC voltage using electromagnetic induction between two coils on a shared iron core.
What is the Transformer formula?
When do you use Transformer?
When solving a transformer problem, first identify the primary and secondary coils and their turn counts N_p and N_s. Then use the turns ratio V_s/V_p = N_s/N_p to find the unknown voltage. If asked about current, apply power conservation: V_p I_p = V_s I_s (assuming an ideal transformer).
Prerequisites
Cross-Subject Connections
How Transformer Connects to Other Ideas
To understand transformer, you should first be comfortable with faradays law and generator.