Big Idea: Magnetism comes to life when conductors carry electric currents.

For instance, ever noticed how two trains on parallel tracks tend to race alongside each other? Now imagine that with two foil strips, but with invisible magnetic fields at play!

• Two conducting foil strips hang vertically.

• Currents can flow in the same direction or opposite directions.

  • If they flow in the same direction: The strips pull towards each other like best friends!
  • If they flow in opposite directions: The strips push away, needing a bit of personal space.
• Pop Quiz: What do you think was used to define the 'ampere' until 2019? Yep, this very effect!

• DIY Alert 🛠️: Fancy trying this at home? Grab

  • Aluminium foil: 3cm wide & 70cm long (two pieces).

  • A power supply up to 25A.

  • Crocodile (or alligator) clips to connect.

Safety first! Those currents are strong, so make sure you handle with care!

It's all about field lines.

• When currents flow in the same direction: Field lines loop around both foils, wanting to be short. It's like two friends holding hands in a circle dance!
• When currents flow opposite: Field lines stand close together between foils, representing a strong magnetic field.

Think of field lines as lazy rivers. They'd rather be short and direct. When foils move closer, they're just helping the field lines have an easier flow!

• Field lines, while often shown as elastic, are NOT actual stretchy bands.

• But why think of them as elastic? It helps us visualize the force direction.

  • When objects move and field lines shorten, work's done! Like pulling a toy car back and letting it zoom forward!

  Tip: Ever struggled to tie your shoelaces and then found an easy but slightly odd way to do it? That's what we're doing when we imagine field lines as elastic!