5J10.20 Back-EMF: Light Bulb
Inductor back-EMF, Faraday's law, Lenz' law
When external current to an inductor is suddenly cut off, the inductor responds by temporarily producing a large EMF that can light a light bulb. In this way, a 6 V battery can momentarily illuminate a 120 V light bulb.
-  Large inductor (~0.5 H)
-  40 W light bulb with socket
-  6 V battery
-  SPST switch
-  Banana cable
-  Insulated alligator clip
- Make sure switch is in the open position.
- Hook up banana cables.
- The inductor is very heavy. Be careful when lifting it.
- Do not short-circuit the battery for a long time.
- Close the switch for about 2 seconds.
- Open the switch.
- PIRA 5J10.20
- Don't attempt this at home!
- Permanent magnet induction
- Solenoid induction with a battery
- AC induction
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.