Transformers and the National Grid

Lab Brief #5

🎯 Your mission

Master the concept. Use it tomorrow.

⚡ The twist

Energy never disappears — it just hides somewhere else.

What you'll learn

A transformer changes the potential difference of an alternating supply using two coils on a shared iron core. Stepping voltage up reduces current for the same power, and because power loss in cables is I²R, high-voltage transmission wastes far less energy.

Key words

transformer
A device that changes the potential difference of an alternating supply.
step-up transformer
A transformer with more turns on the secondary coil, raising potential difference.

Make a hypothesis first

Before you start: which will move faster, and why?

Say your guess out loud — then find out if you were right.

Step 1 of 4 · Read

Think about what you just learned: say what "transformer" and "step-up transformer" mean in your own words before you start.

Step 2 of 4 · Do

Calculate the current needed to deliver 400 kW at 400 V and at 400 kV. Then use P = I²R with a cable resistance of 5 Ω to find the power wasted in each case and express the saving as a percentage.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

Power loss in transmission cables is reduced mainly by:

How sure are you?😐 maybe

Question 2 of 2

A step-up transformer has more turns on the:

How sure are you?😐 maybe

Mind = blown

⚡ Static electricity is the same physics as lightning, just smaller.

Nice work!

You got 0 of 2 right.

Next: Earth's Magnetic Field All lessons

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✨ More to explore

🌍 Where you see this in real life: You use this every time you flip a light switch, ride a bike, or kick a ball.

🏆 Stretch challenge (try it this week): Time how long a small ball rolls down something, then change the slope and try again.

👨‍👩‍👧 For the dinner table: “Show me something at home that uses this kind of energy.”

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