Physics 2020: Fall '12

General Physics 2 (Electricity & Magnetism, and Optics)

MWF 11:00-11:50 Duane G1B20 (Section 100)


A little story about voltages and ancient Pharos of Egypt.

We have discussed how, at a high enough E-field, air "breaks down" and sparks flow from high to low voltages to remove some of the charges responsible for the voltages. When enough charge has built up and the field is strong enough the insulating nature of air will fail and the air will conduct charges which will flow (in the form of lightning bolts, sparks as you shock your sibling, or from a Tesla coil to ground).

This "breakdown" E-field can be lowered with ionizing radiation. Such particles of radiation naturally occur from both the ground and from the atmosphere. When these particles cross a large potential difference they allow sparks to follow their paths. Such path-following sparks have been used to track particles for decades in a piece of equipment called a spark chamber. In a spark chamber like the one shown above, several alternating high voltage plates make large electric fields which spark whenever an ionizing particle passes through them.

Such detectors were used to search the dense Egyptian pyramids for open spaces which would correspond to hidden chambers. Unfortunately, none were found (Here's the original powerpoint.)

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