physics dk Flashcards
electron gun
speeds up electrons with an accelerating pd
- thermonic emission causes electrons to escape coil
- electrons are attracted to anode
KE = 1/2mv^2
VQ = Ve = KE = 1/2mv^2
battery charger
- when battery is flat emf reduces over time
- when you connect a charger with a higher emf to the battery - forcing current into the battery to charge it
rheostat
- can be connected as a variable resistor - good if a large I needs to be vaired
- or as a potentiometer to vary V if current is small
EM waves freq
10^3
10^8
10^12
10^14
10^16
10^20
10^24
EM wave wavelength
10^3 - km
10^-2 - cm
10^-5 - mili-micro
10^-6 - micro
10^-8 - nano
10^-10 - nano
10^-12 - pico
independent vs dependent
independent - x
dependent - y
conditions for equilibrium
resultant force = 0
resultant moments = 0
why is R higher using a battery pack
current is lower
temp of wire/ heating effect is lower
2 improvements to find R experimentally
- repeat with a diff no cells/ variable resistor
- use more sensitve metre
- plot V against I
why electormagnet dropper has a source of error
- not released straught away because of residual magnetism
- can increase distance of fall to reduce
how thinking distance varies with v
TD is prop to speed
aerial why current changes when rotated
if reciever vertical
- electrons are driven up/down the length of aerial - oscillations are vertical causing max I
if horizontal
- electrons driven across the aerial as oscillations are in the vertical field (no oscillation along aerial to cause current) so zero I
rotation by 90 from vertical makes current go from high to low
why can an object in free falls speed not be calulated by v= u + at
acceleration not constant
drag prop to v^2
as v increases so will drag so F will decrease and so will acceleration
galileo and Aristotle
shows constant force is not needed to maintain motion
but force is needed to start/stop/change spped/direction
man in lift eqaution
M(a+g) = F
