Key Practical's

Question 1

Determining the density of solids

Answer 1

find mass / volume
use calibrated scales, callipers and a ruler
resolution of ruler = +- 0.1mm
A volume of irregular volume can be found by immersing it in water then measuring the displaced water

Question 2

Finding unknown masses with moments

Answer 2

Use masses and a clamp stand, moving the masses along and reading lengths then calculate
A spirit level should be used and the ruler is assumed to have uniform density
The extension of the spring would need to be measured with the spring constant

Question 3

Measurement of g by free fall

Answer 3

The electromagnet holds a metal ball then it is turned off and timed till it hit the bottom plate
Take from a range of heights
Plot a graph of t squared against h then gradient x2 = g
We use light gates as well to eliminate human reaction times and use small heights

Question 4

Newtons 2nd law

Answer 4

Use a string with masses attached over a pulley with light gates on the table
Let the masses go one at a time then take them off one at a time attaching to the anchor on the table (mass needs to stay constant)
Repeat and find a graph of a against f to find m
The graph would have a straight line through the origin

Question 5

Youngs Modulus from a wire

Answer 5

Attach a wire to an anchor point with masses off the table at one end , measure initial length
each time mass is added them the wire will extend use markers to show this
Measure this extension and find strain
Use a calliper to find diameter then calculate stress
stress / strain = YM

Question 6

Finding g with a pendulum

Answer 6

Set up a string with a bob on the end from a clamp stand
Hold the bob so it is horizontal and release
count and time 10 oscillations then find average length of one
Each time shorten the pendulum
then plot period squared against L
Inverse gradient x 4pi2 = g
IF the line doesnt go through the origin then there is a systematic error due to not measuring from the centre of the mass

Question 7

Damping of a spring

Answer 7

Attach a string with masses hanging and stretch and release to see how the amplitude varies with each bounce
Add cardboard inbetween each mass and repeat experiment to see the change in amplitude
Plot a graph of log of amplitude against time to see correlation, if you plot A against T then you will get an exponential graph
IF springs are connected in series then the spring constant will DEcrease

Question 8

Specific Heat Capacity

Answer 8

Q = mcT
Use a series circuit connected to a metal block with a thermometer inserted
Record the voltage and the current
Plot a graph of Temp against Time
The immersion heater may take a while to heat all the way through the block

Question 9

Characteristics of a filament lamp and wire at a constant temp

Answer 9

Set up a series circuit with either a filament lamp or nothing
Each time the voltage is increased measure the current
Plot a graph of V against I
For a wire it will be directly proportional
For a lamp it will be positively curved

Question 10

Resistivity of a metal

Question 11

Variation of resistance with temp

Question 12

Internal resistance of a cell

Question 13

Charging and discharging capacitors

Question 14

Energy stored in a capacitor

Answer 14

Set up a circuit with a switch and a joule meter in parallel
Start with a 2V supply and discharge through the capacitor
Repeat for values between 2-12
Plot a graph of energy against voltage squared
Directly proportional

Question 15

Refractive index of a material

Answer 15

Place a ray box at an angle to the glass box, draw an entry and an exit ray for each time the ray box is moved
Plot a graph of angle 2 against angle 1
Angle 1 = Incidence
Angle 2 = Refraction
Snells law can be found from the graph

Question 16

Finding h with LEDs

Answer 16

Set up a circuit with an LED and a resistor (used to stop thermal runaway)
Switch the LEDs around and repeat
Plot a graph of Vmin against 1/wavelength
Gradient x e/c = h

Question 17

Force on a current in a magnetic field

Answer 17

Place a wire through a metal cradle on a scales and attach into a circuit
Every time increase the current by 0.5A and record the mass shown on scales
Plot a graph of force against current
It is directly proportional and the wire needs to be perpendicular to the field

Question 18

Magnetic flux density with a hall probe

Answer 18

create a solenoid and the attach a hall probe at one end
It needs to be placed perpendicular to the field lines
Vhall is proportional to B for all constant currents

Question 19

Variation of gamma radiation with varying distance

Answer 19

Place a gamma source infront of a geiger-muller tube at a set distance.
Measure the background count rate before (5x and take an average)
Each time the radioactivity is measure change the distance between 2-20cm
Plot a graph of count rate against 1/distance squared
This shows the inverse square relationship

Question 20

Determining speed of sound with stationary waves

Answer 20

Place a resonance tube deep within water then gradually raise it at the same time holding a vibrating tuning fork over the top
Plot a graph of length against 1/frequency
A node forms at the closed end of the tube

Question 21

Polarisation

Answer 21

Use a lamp to provide unpolarised light
Place two polarising filters infront of the light, rotating the second one every 90*
Observe the intensity and Plot a graph of Intensity against Angle
This experiment can be used with any transverse wave

Question 22

Find wavelength from youngs double slit experiment

Answer 22

Direct a wave source through a double slit and place a dark surface behind this at distance D
Plot a graph of Fringe spacing against D
The sources must be coherent to superpose

Question 23

Finding wavelength with a diffraction grating

Answer 23

Set up the same to the double slit experiment but with a diffraction grating
The angle can be found from using opp/adj
The screen behind needs to have a matt finish to stop reflection

Question 24

Milikans experiment

Answer 24

Electrons are emitted from the left plate and travel across the gap to complete the circuit and give an ammeter reading
As the voltage is increased the the electrons will be repelled and so the ammeter reading will be 0
The graph of Ek against f will be plotted
Gradient = Plancks constant
y-intercept = Work function