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MIT Physics Demo -- Jacob's Ladder and the Melting Nail

A solenoid is connected to AC power. First, a 10,000-turn coil is placed over the solenoid, but is not connected to the power source. However, the solenoid still induces current in coil, creating very high voltages because of the high number of turns. The rabbit ear spark gap creates an arc that moves from the bottom of the gap to the top (an effect known as Jacob's Ladder). This is due to convection and will not work upside-down

Next, a 1-turn copper loop (containing a gap filled by a nail) is placed over the solenoid. This time the induced current is very large, rather than the voltage. This high current encounters strong resistance in the nail creating temperatures so hot that the nail is melted.

Comments (3)

SUBJECT: MIT Physics Demo — Jacob's Ladder and the Melting Nail

Hi I would like to duplicate your setup for presentation to my students. May I please have the details of your setup and where I can buy parts? Please email me at

Posted over 6 years by Anonymous User

What's the voltage value of the AC source, and how much voltage and current are we talking about that are induced in the secondary coil? — Dishanker Raj

Posted over 6 years by Anonymous User

Hi there, I am interested in presenting a similar demonstration and was after the details of this experiment. Would you please email me ASAP at Thank you very much.

Posted almost 6 years by tmar9082

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April 09, 2008 13:50
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