Veritasium
June 30, 2026
Why Plugs Spark When Unplugged: Electromagnetic Induction Explained
TL;DR
Unplugging a running appliance creates a spark because the sudden loss of magnetic field induces a high voltage that ionizes the air, a principle also used in fast chargers to efficiently convert electricity.
Key Takeaways
- 1A spark requires 10,000 volts, but mains voltage is only 120–240V; the extra voltage comes from electromagnetic induction
- 2When current suddenly stops, the magnetic field collapses and induces a voltage that tries to maintain the current, ionizing air in the gap
- 3Inductors act as shock absorbers in chargers, smoothing choppy electrical pulses into steady DC power
- 4Anker's Embuck technology splits voltage conversion across multiple levels, reducing inductor size to a quarter of standard, enabling compact fast chargers
- 5The same electromagnetic principle that creates sparks is essential to modern power conversion and fast charging technology
Notable Quotes
“Nature hates a sudden change in magnetic field. So it tries to compensate.”
“The inductor resists sudden changes in current. It acts like a shock absorber.”
Chapters
1. The Spark Mystery
Explains the observation that unplugging a running hair dryer produces a visible spark, despite mains voltage being too low to ionize air directly.
2. Electromagnetic Induction
Describes how current flowing through coils creates a magnetic field, and how suddenly cutting that current induces a high voltage as nature resists rapid field collapse.
3. Inductors in Power Conversion
Explains how inductors function as shock absorbers in chargers, smoothing choppy electrical pulses from switching transistors into stable DC output.
4. Anker's Embuck Technology
Details how Embuck technology splits voltage conversion across multiple levels and switches at 200,000 times per second, reducing inductor size to enable compact 160W fast chargers.
Key People & Entities
- Anker
- Sponsor; manufacturer of fast chargers using Embuck technology
Glossary
- Electromagnetic induction
- The process by which a changing magnetic field induces an electrical voltage in a nearby conductor
- Inductor
- A coil of wire that resists sudden changes in current and stores energy in a magnetic field
- Ionization
- The process of adding or removing electrons from an atom, allowing air to conduct electricity and create a spark
- Embuck
- Anker's proprietary technique that splits voltage conversion across multiple levels to reduce inductor size and enable compact fast charging
- DC (Direct Current)
- Electric current that flows in one direction, used to power devices like phones and laptops