Why these experiments matter 🌍⚡

Life with light bulbs, trains, phones, and laptops exists because we know how to generate electricity. The turning point came from the clever lab-work of Michael Faraday and Joseph Henry, which showed that motion plus magnetism → electricity :contentReference[oaicite:0]{index=0}.

Experiment 6.1 – Moving Magnet, Stationary Coil 🧲➡️🔄

  • A single coil C1 is wired to a sensitive meter (galvanometer).
  • Push the N-pole of a bar magnet toward the coil ⇒ meter needle jumps right. Pull it back ⇒ needle jumps left. No motion, no current :contentReference[oaicite:1]{index=1}.
  • Swap to the S-pole and every deflection flips direction.
  • Faster motion ⇒ bigger kick on the meter (larger induced current).
  • Hold the magnet still but move the coil – same story! Key idea: only the relative motion counts.

Experiment 6.2 – Two Coils, One Battery 🔋🔁

  • Replace the magnet with a second coil C2 carrying a steady current (thanks to a battery). That current sets up a steady magnetic field :contentReference[oaicite:2]{index=2}.
  • Shove C2 toward C1 ⇒ meter deflects; pull it away ⇒ deflection reverses.
  • If the driver coil pauses, the meter in C1 goes quiet.
  • Again, nudging either coil works the same – “relative motion” wins.

Experiment 6.3 – Changing Current, No Motion 🎚️⚡

  • Both coils stay put. C2 connects to a battery through a tap-key K; C1 remains on the meter :contentReference[oaicite:3]{index=3}.
  • Press K (switch on): meter in C1 gives a sharp twitch, then returns to zero even though current in C2 continues.
  • Release K (switch off): twin twitch in the opposite direction.
  • Slide an iron rod inside the paired coils – the twitches grow! (Iron channels the magnetic field, boosting the effect.)
  • Lesson: Motion is not essential; any change in the linked magnetic field (here, created by switching current) sparks an induced current.

Magnetic Flux \( \Phi_B \) 🌐

Faraday wrapped these demos into one clear picture: what really matters is how much “magnetic stuff” (magnetic field lines) pierces the coil. That amount is called the magnetic flux \( \Phi_B \) :contentReference[oaicite:4]{index=4}. Whenever \( \Phi_B \) through a circuit changes, nature answers with an electric current.

High-Yield Ideas for NEET 📌

  1. Relative motion principle: Moving a magnet past a coil or a coil past a magnet creates current. Speed upswing ⇒ bigger current.
  2. Polarity & direction: Swap N ↔ S or reverse the motion direction and the induced current flips.
  3. Mutual induction: A time-varying current in one coil kicks up an induced current in a nearby second coil.
  4. “Change” is crucial: Steady situations (magnet held still, battery current unchanging) give zero induced current; only a changing magnetic environment works.
  5. Magnetic flux view: All three demos echo one rule— change the flux \( \Phi_B \) linking a circuit and an emf pops up. That concept underpins Faraday’s law you meet next.

✨ Keep exploring—these simple lab tricks power every generator you see today! ✨