2021 Paper 3 Flashcards
With decay questions, if something si proprtionsl to another, how can you make new equation
If A is proportional to P, and this goes for everything , then can replace A with P
How would power be if each decay release energy equation
Power = activity x ke
As p = wd /time, and activity is number / time , so it works!
If it asks for a table, what to ensure
Remember write down EVERYTHING that changes or needs to be plotted
So even the ln column!
How to keep LDR experiment accurate
Different ways
Keep ambient light the same
Keep everything the same distance, do this by clamping
Keep temp CONSTSNT by using fand
Don’t cast YOUR OWN SHADOW on to the ldr
Remember total energy of gpe and v
Is negative gpe + ke
And if it gains ke, gpe beocmes less and thus further away
How to draw magnetic field lines
MUST DRAW COMPLETE CIRCLES from start to finish, thst way guarantee get marks
They want to see the mag fields inside the coil most of the time too not outsode
Explain the origin of this large current
What’s the difference between where emf is induced snd current, can you say current? If not where does it come from
NO can only say magnetic EMF is induced, the v
However ofc there is a pd involved too there will be a current
The current is a result of the resistance , and so for whatever pd , it is derteimed by resistance
Therefore if resistance is low this the only way current will be too! Thus must say low resistance in conductor being induced
Don’t make mistake, any hand that has some conductance will experience the SAME emf induced
However what changed the fact thst it’s safe?
Okay so what shape ign is current Heats up
Your hand will experience the same emf induced ! ( why wouldn’t it, it’s not depenednt on material but rste of flux, this is constant so it will be induced same amount )
However they have EXTREMELY HIGH RESISTANCES DUE TO BEIGN INSULATORS. Remember resitivity for insulators is low…
Therefore the current will be very small, even for same emf! So not dangerous
So yeah current induced is diff to emf
Therefore
In a question , why does there have to be friction for fc
Remember what is fc
Fc is the resuktsnt force. Which MUST act to the centre at all times
Sometimes the direction of resuktsnt is not always vertical hence must be component in horinxtal plane
As weight and reaction are vertical only, this means there must be friction acting, to provide horizontal component for fc, as this can’t be provided by vertical resuktsnt!
Fir these qs, how to find the resulting graph
See where they took their angle from and determine the directions
The angle will tell you cos or sin , and direction will tell you left or right
Don’t be tricked into random other angle
Kinetic theory of gas describes what
How to use it to show what higher temps will do to particles that can escape
This is that using ideal gas assumptions
- pressure = force / area
- force is caused by rste of change of momentum
- as gasses have ideal elastic ollsiojs rate of change is -2mv / time
- the sum of all these forces over an area is the pressure
Effect of increasing temp
- would be that the particles collide faster and more frewuency, which would lead to greater force and thus pressure
However as PRESSURE CONSTANT , this means that a,though harder Collisons, less must occur to keep oressure constant
- this only happens if particles leave
- so even tho increase in temp increases ke per particle, as N decreases, and total ke = 1/2 NMc2 , this balances out
What is total ke
Ke one x N
So 1/2N mc 2
How to show the total internal ke stays constant
Find an equation that eliminates temlertaure
And show constants
Show that at diff temp what happens to things
And thus stays constant
The fsct that increaseing temp decreases moles, show that this is constant, hence ke must be constant too
Remember energy fo whole gas equations
E = N Inclusive
So although energy of single gas drops, more n means same
Always put formual down in case you gain amrk
