Equipment:

• Mini tesla coil
• Mini fluorescent tube light bulb
• Demonstrator (only experienced instructors should do this alone!)

Demo:

1. Place the Tesla coil far from any conducting objects, laptops, and people (at least a few feet away).
2. Dim the lights
3. Plug the coil in to supply power.
4. Turn the knob at the base of the coil clockwise to turn on
5. Hold the fluorescent tube approach it to the coil. It will light up! DO NOT hold the metal contacts and do not touch it to the coil.

Explanation:

When the tesla coil is plugged into a wall socket, the electricity flows through a iron core that is hollow on the inside and is wrapped with copper wire on the outside. This piece then becomes electromagnetic. It is called the vibrator. The buzzer consists of two tungsten contacts that are not touching. They pull apart when the electromagnet is turned on and then closes when the field decays. This occurs 120 times per second due to the AC current changing the polarity of the electromagnet. The capacitors then charge as the buzzer contacts are open. The open contacts allow the air in between the spark gap to be ionized, thus shorting the circuit. However, the capacitors will keep their charge. Unseen by the eye, the spark between the gap is actually multiple shocks transferring charge back and forth. The electromagnetic field is formed by the primary, which uses the stored charge from the capacitor when the iron core decays. A charge of higher voltage is created every half cycle of the AC current. The sparker also acts in the same way. The capacitors act as storage for charge and as a high pass filter. The capacitors block low frequency 60 cycle current. This is also a safety feature.The result of this process creates of generating high frequency electrical energy through the decay of B fields every half cycling, often creating many millions of cycles per second.

When the frequency is high voltage is great enough, determined by the size of the capacitor, the primary coil induces a magnetic field in the secondary. This is done using resonance. When the primary is tuned properly to the secondaries resonant frequency a high frequency is output of about 50,000Volts is created

Diagram from Scientific First

In one form or another a Tesla coil is a high-voltage generator. it has a long solenoid  with length l and cross section area A which is  wound with N¹ turns of wire. Another coil of wire has N² turns around it. A current I¹ in the solenoid sets up a magnetic field B¹ at its center. The equation forB¹ is given below:

The flux for the cross section equals B¹A. Since the solenoid is long it produces no magnetic field outside of its coil, which is also equal to  . No matter the area of the outer cable  the mutual inductance is always M, which is given below:

The mutual inductance only depends on the geometry of  the two coils, not the current.

Notes:

• Caution: This apparatus is dangerous for people with pacemakers, and could damage computers or sensitive equipment. Keep coil several feet away from the nearest observer!