Physics
Kevin MehallApplications of electromagnetism
8.02 Lecture 19The heart
-80mV inside heart cells
Electric field across cell wall
Goes to +20mV when activated
polarization wave travels downward, causing muscle to contract
then depolarization wave travels up, returning original charge and causing muscle to relax
Wave transfers by moving ions in and out of cells
Creates dipole field
Electrocardiogram measures potential difference caused by this field
defribulators / pacemakers
Aurora Borealis
Electrically charged particles spiral around magnetic field lines
Solar wind contains charged particles, which are guided into north/south poles by earth's magnetic field
Interact with nitrogen/oxygen to create light
Superconductivity
Impossible to have an electric field in a superconductor
When approached by a magnet, emf must remain 0, so eddy currents will flow to never allow magnetic flux
superposition of 2 fields squeezes the field around the superconductor
magnetic pressure P = \frac{B^2}{2\mu_0} [N/m^2]
eddy current will always repel magnet, no matter what orientation
Maglev train
magnet moving over conducting plate also creates similar magnetic pressure
AC Current through coil over plate works similarly and doesn't have to move
