physics dont know Flashcards
best emitter /absorber
matt black
voltage
energy transfer per unit charge passed
filament lamp graph / explanation
atoms in filament vibrate causing more collision with electrons slowing them down increasing resistance
thermistor/ ldr graph or explanation
heat / light energy releases more free electrons to flow
downward force
is weight NOT GRAVITY
continuous data
measurable range of values
discrete data
separate values you count
oscilloscope method to find freq
- connect to microphone
- adjust time base to get a complete cycle on the screen
- measure no. squares for 1 cycle
- times by time base
- use f = 1/t
absolute magnitude
-5 - brightest
0
+5 - least bright
atmospheric pressure
100kPa
necessity of control rods
- without there will be too many neutrons
- too many fissions
- too much energy - melts down
energy released in fission as
movement of daughter nuclei
why wind / rain could cause rollercoaster roll back
wind - air resistance increases
wet - sloppy - less energy transfer to car during launch
higher refractive index
more bending
virtual image
- can be formed on screen
- rays don’t acc come from there
an optical image formed from the apparent divergence of light rays from a point,
as opposed to an image formed from their actual divergence
how can you tell from a diagram there is a virtual image
rays don’t actually meet at image
TIR conditions
i>C
more dense to less dense
why reflected waves received for longer
- reflected from diff depths
- pulses travel diff distances
ac effect on field made
weaker magnetic field as it’s changing direction
why newton meter is wrong
scale too small to show actual value
temp reaches steady level when heated why?
- heat is lost to surroundings
- rate of loss = rate of supply
why transformers have soft core
easily magnetised and demagnetised
magnetic field changes so has to be able to magnetised and demagnetised easier
transformer method
- steps up/ down V
- current in coil1 makes magnetic field
- current is changing ac
- field changes
- core strengthens field
- field interacts with coil2
- inducing V in coil2
why curved magnet is better for motor
- force is increased (stronger field)
- radial magnet acts in all directions
- coil remains in field for long time
how to use radioactivity to date bones
- living things all contain carbon
- C14 is radioactive
- over time radioactivity decreases
- know half life of C14 from other sources
- can see how long since it was alive (how many half lives)
positives of high voltage transmission
- lower current as VI= VI
- more efficient as less energy used so less pollution
- transmits energy further eg national grid
- uses thinner cables
- less heating by high I so less power loss
why does pressure act in all directions
- particles move at random
- collide with all walls
- force per unit area is same on all sides of the cylinder
why is a moons gravitational force less if it has a bigger mass
- larger radius
- lower density
- smaller core
electric current
rate of flow of charge
red vs blue light refraction
- longer wavelength means less bending so red is refracted less
irridation
- radiation hits object
- object not radioactive
- can be shielded
- stops when source removed
contamination
- source is in/ on an object
- object radioactive as long as source is in it
- can’t be blocked
- hard to remove
R in series
Rt = R1 + R2
if adding a component resistance increases
R in parallel
Rt = Vt/ It
if adding component total resistance decreases
