2:01 these two interactions were fundamentally related
2:04 as it turned out they were both the product of charge
2:07 charge is an analog mass
2:10 like mass charges an inherent property of matter that is associated with the
2:15 fundamental interaction
2:16 mass produces gravitational fields in these fields cause mass is to attract
2:21 one another
2:22 similarly charge produces electric fields
2:25 which interact with other charges by causing them to either attract or repel
2:29 the concept to fields can be somewhat counterintuitive
2:32 so it might be helpful to think of them as odors the closer you are to the
2:36 source
2:37 have an odor the more strongly you feel its effects if you dislike the older
2:41 you'll tend to move away from the source but if you find the older attractive
2:45 you'll turn to come in closer electric fields work analogously
2:49 obvious the charges will be pulled toward each other because their fields
2:53 her odors attract one another like charges will move away from each other
2:57 because their fields repel them
2:59 when these charges begin to move they generate magnetic fields
3:03 which further affect the motions have other charges additionally
3:07 it was discovered that not only to change in electric fields generate
3:11 magnetic fields
3:12 but changing magnetic fields will also produce changing electric fields
3:16 moving a charged particle will produce magnetic effects
3:20 moving a magnet
3:21 will generate electric voltage taken together
3:24 what this all suggests is that electricity and magnetism
3:27 are different aspects have the same force the theory of electromagnetism
3:32 involved many difficult derivations and meticulous experiments
3:36 but when the dust finally settled it became clear to all that not only are
3:40 electric and magnetic phenomena fundamentally the same force
3:43 but that electric and magnetic fields could together
3:47 produce a wave a wave is a disturbance that travels through some material
3:51 called a medium when this string experiences an impulse
3:55 a disturbance passes through it the same general principle applies to sound waves
4:00 which in the common case are a disturbance passing through air
4:03 molecules
4:04 waves at the beach are also based on the same concept
4:07 disturbances passed through the water manifesting themselves and is familiar
4:11 forms
4:12 was crucial to recognize is that in each case
4:15 the medium itself the string the air molecules the water
4:19 is not moving from one end to the other they're simply being displaced by the
4:24 energy that's passing through
4:26 so what happens when you take an electric charge
4:29 and start to shake it back and forth analogously to the way this boy is
4:32 shaking the string