MOTION MOUNTAIN

54 1 electricity and fields
TA B L E 13 Voltage values observed in nature.
Observation
Voltage
Page 92
Smallest measured voltage
Human nerves
Volta cell
Voltaic cell (‘battery’)
Mains in households
Electric eel
Tramway supply
Sparks when rubbing a polymer pullover
Electric fence
Train supply
Ignition plug in cars
Colour television cathode ray tube
X-ray tube
Electron microscopes
Stun gun
Lightning stroke
Record accelerator voltage
Maximum possible voltage in nature (corrected Planck voltage√ħc 5 /4G/e )
c.10 fV
70 mV
1 V
1.5 V
230 V or110 V
100 to600 V
500 V
1 kV
0.7 to10 kV
15 kV
15 kV
30 kV
30 to200 kV
0.5 kV to3 MV
65 to600 kV
10 to100 MV
1 TV
6.1⋅10 27 V
duced asamathematical tool, though,for thedescriptionof materials.) The strengthof
magnetism, used in any running electric motor, proves relativity right: there is a maximumspeedinnatureforallmassesandcharges.Bothelectricandmagneticfieldscarry
energyandmomentum.Theyaretwofacesofthesamecoin.
Curiosities and fun challenges about things electric and
magnetic
“Aliiveroetfactamiratietintellecta assecuti.*
AugustineofHippo”
Beforewestudythemotionofanelectromagneticfieldindetail,let’shave some fun with
electricity.
∗∗
Nowadays, having fun with sparks is straightforward. Tesla coils, named after Nikola
Tesla** are the simplest devices that allow long sparks to be produced at home. Atten-
* ‘Others however marvelled about the facts and understood their meaning.’ Augustine, Sermon 98, 3.
Augustine of Hippo (b. 354 Tagaste, d. 430Hippo Regius) is an influential moral theologian. Despite this,
hedidnottakecareofhisextramarital son,norofhisson’smother,becausehisownmotherhadforbidden
himtodoso.
** Никола Тесла (b. 1856 Smiljan, d. 1943NewYorkCity), engineer and inventor. He invented and pro-
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net