12th of may learn em Flashcards
(46 cards)
is magnetic flux density?
strength of a magnetic field
unit of magnetic flx density
tesla
tesla definition
1 tesla is when a wire perpendicular to the field with a current of 1 amp experiences a force of 1 newton per metre of length
what is the symbol for magnietic flux density
B
whats a couple
pair of forces that are equal, acting in opposite directions and parallel
whats a torque
the moment of a coupe
equation for torque
one of the forces X perpendicular distance between forces
equations for upthrust
upthrust =Axpg (Ax is volume of water displaced)
Archimedes principle
upthrust exerted on a body Immersed in fluid, partially or fully submerged, is equal to the weight of fluid displaced
whats the ultimate tensile strength
maximum stress a material can withstand before it breaks
whats a semiconductor
component with a negative temperature coefficient. resistance drops as temp increases
what is intensity proportional to
amplitude squared
whats the intensity of something with a radiant power spreading out in a sphere
P/4pi r^2
conditions for TiR
- light travelling in a medium with a higher refractive index and strike a boundary with a medium with a lower refractive index
- angle it strikes at boundary must be bigger than the critical angle
electronvolt definition
energy transferred to or from an electron when it is accelerate by a potential difference of 1 volt
equation to find plancks constant
use LEDs. plot graph of threshold voltage against 1/wavelength of light emitted. find gradient and do some maths
whats the work function
minimum energy required to emit an electron from the surface of a metal
how to find the threshold frequency
work function = hf0 because kinetic energy of emitted electron would be 0
specific heat capacity definition
energy required per unit mass to change the temperature of a substance by 1 kelvin
whats specific latent heat?
energy required to change the phase per unit mass whilst at a constant temperature
what is free oscillation
a system that is displaced and allowed to oscillate without any external force is free oscillation
what is natural frequency
the frequency of the free oscillations of the oscillator
what is driving frequency
the frequency an oscillator is made to oscillate at by a periodic driver
when will something resonate
when the driving frequency is equal to the natural frequency