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Change the turns on a transformer. Can you make the street lamps brighter, or blow them?
Power to the Town lab · Last updated: 16 October 2026
A transformer feeds the street lamps of a model town. You change the number of turns of wire on each side and watch the lamps glow brighter, dimmer or blow out. It shows how electricity is sent safely across a country.
What you'll discover
- A transformer changes an alternating voltage up or down using two coils of wire.
- The ratio of turns on the two coils sets the ratio of the voltages.
- Too high a voltage for a lamp makes it too bright and can blow it.
The science in plain words
A transformer has two coils of wire wound on the same iron core. Alternating current in the first coil, the primary, makes a magnetic field that keeps changing direction. The iron carries this changing field through the second coil, the secondary, where it induces a voltage. This is electromagnetic induction, so transformers only work with alternating current.
The voltage you get out depends on the number of turns on each coil. If the secondary has twice as many turns as the primary, the voltage doubles: a step-up transformer. If it has half as many, the voltage halves: a step-down transformer.
Energy is not created. If the voltage goes up, the current goes down in the same proportion, so power in roughly equals power out. Real transformers lose a little energy as heat.
This is why power companies use transformers. Sending electricity along long cables at very high voltage and low current wastes much less energy as heat in the wires. Near homes, step-down transformers bring the voltage back to a safer level, around 230 volts in India and 120 volts in the United States. Phone chargers contain small step-down transformers too.
Where it fits
- India, NCERT: Transformers are taught in NCERT Class 12; this lab builds on Class 10 Chapter 11: Electricity and Chapter 12: Magnetic Effects of Electric Current.
- United States: Grades 9 to 12
- Next Generation Science Standards: HS-PS2-5
Common questions
What does a transformer do?
It changes the voltage of an alternating current, stepping it up or down. It uses two coils of wire on an iron core, and the ratio of their turns sets how much the voltage changes.
Why is electricity sent at high voltage?
At high voltage the same power needs much less current. Less current means much less energy wasted as heat in long cables, so high voltage is more efficient for long distances.
Why don't transformers work with batteries?
Batteries give direct current, which makes a steady magnetic field. A transformer needs a changing magnetic field to induce a voltage in the second coil, so it needs alternating current.
Related labs
- Magnet Drop: Drop a magnet through a coil of wire. Can a falling magnet make electricity?
- Bike Dynamo: Pedal a bike on a stand. How does turning a magnet light the lamp?
- Simple Circuits: Close the switch. What makes the bulbs brighter: more volts, fewer bulbs, or a different wiring?
See all physics labs or every Taz science lab.
Try it yourself
The Power to the Town lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.