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Code Number: 5B30.35
Demo Title: Corona Discharge
Condition: Excellent
Principle: Corona Discharge, Surface Charge Density
Area of Study: Electricity and Magnetism
Equipment:
Van de Graaff Generator, Ball with Retractable Metal Spike.
Procedure:
Set the apparatus as shown. Retract the metal spike and start the generator. Notice that there is charge buildup but no arcing between the spheres. Stick the spike out of the ball and point towards the generator and note the arcing. Turn the spike away from the generator and observe the corona. This is best observed in a darkened room. Refer to Eb - 2 for charge sign information. In our case the Van de Graaff generator should have a negative charge.
A much easier way to demonstrate corona is to put the pinwheel onto the point of either of the two larger Tesla coils. Very nice corona will be visible at each point of the pinwheel.
References:
- Richard E. Orville, "The Lightning Discharge", TPT, Vol. 14, # 1, January 1976, p. 7.
- Eb-2: Freier and Anderson, A Demonstration Handbook for Physics.
- J. B. A. Mitchell et al., "Nanoparticles in Ball Lightning", Physics Today, Vol. 61, # 2, Feb. 2008, p. 18.
- E. Philip Krider, "Benjamin Franklin and Lightning Rods", Physics Today, Jan. 2006, p. 42.
- Jearl Walker, "5.21, St. Elmo's fire and Andes Glow", The Flying Circus of Physics Ed. 2, p. 228.
- Jearl Walker, "5.7, Lightning Rods", The Flying Circus of Physics Ed. 2, p. 221.
- Jearl Walker, "3.56, Thunder", The Flying Circus of Physics Ed. 2, p. 168.