The ratio of turns on the two coils fixes the ratio of the voltages exactly. Add the rule that power in equals power out, and a transformer becomes a precise tool, and the reason the grid runs at hundreds of thousands of volts.
For an ideal transformer the voltage ratio equals the turns ratio: Vp divided by Vs equals Np divided by Ns. If power is conserved, Vp times Ip equals Vs times Is. High-voltage transmission uses a small current, so the cables waste far less power as heat.
For an ideal transformer, the ratio of the voltages equals the ratio of the turns, and the input power equals the output power.
Transmitting at high voltage gives a low current, and the power wasted in a cable is current squared times resistance (I²R).
Change the turns ratio and watch the secondary voltage and current follow the equations.
Four quick checks. Each correct answer earns XP and lights this skill on your star map.
For a transformer, Vp ÷ Vs equals...
For an ideal transformer, the input power equals...
Power is transmitted at high voltage so that the current is...
The power wasted as heat in a transmission cable is given by...
A higher transmission voltage means a smaller current, and the cable loss falls steeply.
A transformer has 200 turns on the primary and 50 on the secondary. The primary voltage is 240 V. Find the secondary voltage.
In the National Grid the voltage is stepped up for transmission so the current is small, because the power wasted in the cables is the current squared times the resistance. A smaller current means far less heat lost.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
A transformer has 200 primary turns and 50 secondary turns. With 240 V on the primary, the secondary voltage is...
An ideal transformer has a primary at 240 V drawing 2.0 A. The secondary is at 60 V. The secondary current is...
Raising the transmission voltage and lowering the current reduces energy loss because the cable loss depends on...
Transformer equations complete the electromagnetism strand and Unit 4. Keep the chain going.