Practicals Flashcards
What is the equipment needed for using light gates to determine g
● Clamp stand
● Electromagnet connected to low voltage DC supply
● Steel ball bearing
● Light gates x 2
● Data logger
● Metre ruler
● 2 kg counterweight
● Soft pad for the ball bearing to land on
What is the method of using light gates to determine g
- Set up a clamp stand, with an electromagnet connected with a low voltage DC supply. Have the steel ball baring on the electromagnet and have the light gates a distance h(m) with a pad underneath.
What is the calculations of using light gates to determine g
Plot a graph of 2h against t^2
and draw a line of best fit. The gradient of the line of best
fit will be g. This is derived using one of the constant acceleration formula below:
s = ut +1/2 at^2
h = 1/2 g t^2
What is the safety of using light gates to determine g
● Use a counterweight or clamp the stand to the table to avoid it toppling over and
causing injury.
● The ball bearing is cushioned by a pad at the bottom of the clamp so it does not
bounce upwards and cause injury.
● The distance between the upper light gate and the starting position of the ball bearing
must be kept constant so that it reaches the upper light gate with the same speed
each time.
● The ball bearing should be dense to help mitigate the effects of air resistance.
● To reduce parallax error in measuring the height, a ruler can be clamped directly next
to the light gates.
● You could use the light gates to record the initial velocity (u), final velocity (v), and the
time taken for the ball bearing to fall between the gates. This would allow you to use
the constant acceleration formula v = u + at to calculate g. Note the values of
velocity would be averaged as the bearing is accelerating while moving through the
gates.
What is the equipment needed for using stopwatch to determine g
● Tennis ball
● Stopwatch
● Metre ruler
● Soft pad for the ball to land on
What is the method needed for using stopwatch to determine g
- Using the metre ruler, measure a height (h) of 1.0 m. Place the soft pad at the bottom
of the ruler. - Hold the tennis ball so the its bottom half is at the 1.0 m mark (it may be useful to
work in pairs here, one holding the ruler, one holding the ball). - Release the ball and simultaneously switch on the stopwatch and switch it off as
soon as the ball hits the soft pad. Note the time taken for the ball to hit the ground (t)
as recorded by the stopwatch. - Reduce h by 0.05 m and repeat the above two steps, reducing h by 0.05 m each time
down to 0.50 m. - Repeat the experiment twice more to find mean values of t for each value of h.
What is the calculation needed for using stopwatch to determine g
Plot a graph of 2h against t^2
and draw a line of best fit. The gradient of the line of best fit will be g
What is the saftey needed for using stopwatch to determine g
- The ball bearing is cushioned by a pad at the bottom of the clamp so it does not
bounce upwards and cause injury. - The metre ruler must be kept perpendicular to the ground, you could use a set
square to make sure this is the case.
The tennis ball will experience a large amount of air resistance which may affect your
calculation of g, therefore the tennis ball can be swapped out for a ball bearing to
improve results.
● Reaction times will hugely affect the recorded times (t), making the results less
accurate
What is a comparison of the light gate method and stopwatch method in order to determine g
The second method is easier to carry out and requires less complex equipment, however it
will be far less accurate. Therefore, the initial method is better for calculating a more
accurate value of g
What is the equipment needed to learn to investigate terminal velocity
● Long plastic tube
● Elastic bands
● Ruler
● Clear viscous fluid
● Steel ball bearing
● Stopwatch
● Strong magnet
What is the method needed to learn to investigate terminal velocity
- Wrap elastic bands around the tube of viscous liquid at set intervals measured by the
ruler. - Drop the ball into the tube and record the time it reaches each band (it will help to
use a lap feature on the stopwatch here). - Repeat 4 times to reduce the effect of random errors and use the strong magnet to
remove the ball bearing from the bottom of the tube.
What is the calculation needed to learn to investigate terminal velocity
● Calculate the time taken to travel between consecutive bands and calculate the
average of this time for each experiment.
● Use the equation speed = distance/time to find the average velocity of the bearing
between each set of bands.
● Plot a graph of velocity against time. The velocity to which the graph tends to is the
terminal velocity.
What is the safety needed to learn to investigate terminal velocity
● Use a viscous liquid that doesn’t cause skin irritation
● Using a taller tube allows the bearing to travel at its terminal velocity for longer.
● Using larger intervals for the bands reduces the percentage uncertainty in both the
distance and time between the bands.
● Terminal velocity occurs when the weight of the bearing is equal to the drag force
due to the fluid, as there is no resultant force on the bearing, it travels at a constant
velocity.
What is the equipment needed to learn to investigate initial speed and stopping distance
● Meter ruler
● Wooden Blocks
● Light gate
● Interrupter card/piece of card 10x10cm
What is the method needed to learn to investigate initial speed and stopping distance
- A vehicle is modelled by the block of wood which is pushed and decelerates due to friction
with the surface it moves on. - Glue the 10 x 10 cm interruptor card to the side of the block of wood so that the time for the
width of the card to pass through the gate is recorded. The interruptor card allows the
distance moved through the light gate to be fixed, as it registers with the light gate easily
without the light gate interrupting the block’s motion. - Set up the light gate such that it records the average starting velocity of the block moving
through it (speed = 0.1 m/time for card to move through in seconds). - Record the starting position of the block and position the light gate 2 cm after this point.
- Push the block and record the position at which it stops.
- Record the average starting velocity and the corresponding distance between the light gate
and the stopping point (stopping distance), in a table.
What is the calculations needed to learn to investigate initial speed and stopping distance
● Find the stopping distance for a range of starting velocities.
● Plot a graph of stopping distance against starting velocity squared, this should be a straight
line through the origin as:
E of the block = 1/2 mv^2
As all the kinetic energy is converted to thermal energy by frictions
E = force X stopping distance.
v^2 ∝ stopping distance
What is the equipment needed to calculate youngs modulus
● G-clamp
● Wooden blocks
● Long copper wire
● Tape
● Metre ruler
● Work bench
● 100 g masses
● Pulley
What is the method needed to calculate youngs modulus
Set up a work bench with a wire being pulled on one end with a pully and masses and on the other side a G-clamp and wooden blocks. Measure the diameter of the wire in 3 different places using a micrometer and record these
values (how to use a micrometer is illustrated below).
Attach the metre ruler to the workbench so that the lower end is facing the G-clamp and
place a marker on the wire at 0 cm on the ruler.
Measure the length of wire from the blocks of wood to the marker on the wire when it is taut
Attach a mass to the wire and record the total mass attached to the end of the wire in kg.
The wire will stretch when this mass increases therefore, record the new position of the
marker.
Add another 100 g mass and once again record the position of the marker, keep doing this
until you have readings for at least 7 mass values
What is the calculations needed to calculate youngs modulus
● Find the mean diameter of the wire and calculate the average cross sectional area using
A = (πd^2)/4
● Using F = mg calculate the force exerted on the wire for each mass and record these
values in a table
● Calculate the wire’s extension by finding the difference between the marker’s final position
and its initial position for each mass
● Find the stress for each mass by dividing the force applied by
the cross sectional area of the wire
● Find the strain on the wire for each mass by dividing the
extension by the original length of the wire ΔL
● Plot a graph of stress against strain and draw a line of best fit
● As the Young modulus = stress/strain, the gradient of the line of
best fit is equal to the Young modulus of copper
What is the saftey needed to calculate youngs modulus
● You MUST wear protective eyewear, as if the wire snaps and flies out it could seriously
injure or blind people near it.
● Place some cushioning under the masses in case the wire snaps so that they will not
bounce and hit people’s feet if they fall.
● Make the original length of the wire as long as possible because this will reduce the
uncertainty in the measurement of original length.
● Make sure the wire is relatively thin because the thinner the wire, the larger the extension it
experiences. A larger extension will reduce the uncertainty in the measurement of
extension.
● Try and find the extension for as many masses as possible as more data points allows a
better line of best fit to be drawn.
What is the equipment needed to Investigating springs in series and in parallel
● Stand and clamp
● Springs
● Metre ruler
● 50 g masses
What is the methods needed to Investigating springs in series and in parallel
For springs in series
Set the springs in series
1. Record the original length, L of the spring(s) and the
number of springs in the series, n.
2. Attach the mass and record the new length of the
springs.
3. Repeat for different values of n.
For springs in parallel
Set the springs in parallel
1. Record the original length of the springs in parallel.
2. Attach the mass and record the new length of the springs.
3. Repeat for different numbers of springs in parallel.
What is the saftey needed to Investigating springs in series and in parallel
● Do not exert too high a force on the springs as if part of the apparatus breaks then the
masses will fall and can cause injury.
● Don’t let the springs recoil too quickly as they can snap on fingers and cause cuts and
bruises.
● Wear eye protection.
● Using too high a force can cause the springs to become permanently extended.
● Always measure the spring’s position from the same point, if it helps, mark this point with
pen or tape.
What is the equipment needed to investigate a property of plastic
● Plastic bag
● Guillotine
● 100 g masses
● Holepunch
● Ruler
● Stand and clamp
What is the method needed to investigate a property of plastic
- Using the guillotine slice the plastic bag both lengthways and widthways to test its
properties in each plane (separate these sections so that they don’t get muddled up). - Holepunch one end of each strip to create a hole to hang the masses from.
- Attach the strip to a clamp stand and measure its original length (while taut) from
where it is attached to the clamp stand to the hole where masses will be attached. - Attach a 100 g mass to the strip of plastic and measure its new length.
- Repeat this process the above step, measuring the new length until you have taken
at least 10 readings of extension for a given mass. - Apply this method to the other strips, recording whether they are width ways or length
ways strips. For the strips that do not break, rather than beginning a new strip,
remove the masses one by one recording the new length after each removal. This
unloading will allow an unloading line to be plotted on the force-extension graph.
What is the calculations needed to investigate a property of plastic
● The table that the results are recorded in and calculations are carried out in, has the
headers illustrated below.
Mass, Force, Original Length, New length, extension
Extension is found by the difference between the new length and original length.
Force applied is calculated using the product of mass and g (acceleration due to
gravity).
● Plot a graph of force against extension. This graph will show properties of the plastic,
for instance:
○ Limit of proportionality - the point after which Hooke’s law is no longer
obeyed (force is no longer proportional to extension)
○ Elastic limit - if you increase the force applied beyond this, the material will
deform plastically (be permanently
stretched).
○ Breaking stress is the value of stress at
which the material will break apart, this
value will depend on the conditions of the
material e.g its temperature.
○ The area between the loading and
unloading line represents the work done
to permanently deform the material
What is the safety needed to investigate a property of plastic
● Using a holepunch means the force isn’t evenly distributed through the stip but
concentrated by the hole - using a bulldog clip wound around the bag allows more
even distribution of the weight of the masses.
● Using a computer and spreadsheet software for the table can save time as extension
and force can be calculated immediately and without error.
● Read the ruler at eye level to avoid parallax error.
● Cushion the floor below the masses and be wary of them falling.
● Be careful when using the guillotine.
what equipment is needed to determination of resistivity of a wire using a micrometer,
ammeter and voltmeter
● 1m long constantan (copper–nickel alloy) wire
● Voltmeter
● Ammeter
● Low voltage power supply
● Micrometer
● Metre ruler
what method is needed to determination of resistivity of a wire using a micrometer,
ammeter and voltmeter
- Connect a battery, ammeter, voltmeter and length of wire L
1. Measure the diameter of the constantan
wire at 3 points along its length using the
micrometer, and calculate the mean
diameter.
3. Adjust length l to 10 cm using the crocodile
clips and metre ruler.
4. Read and record the current (I) on the
ammeter and the voltage (V) on the voltmeter. Calculate the resistance (R) by using
R=V/I and record this value.
5. Switch the circuit off in between readings to prevent heating of components which
could affect their resistance.
6. Increase l by 10 cm and repeat the above two steps, increasing l by 10 cm each time
up to 80 cm.
7. Repeat the experiment twice more, then calculate the mean resistance for each
length.
what safety is needed to determination of resistivity of a wire using a micrometer,
ammeter and voltmeter
● Disconnect the crocodile clips in between measurements to avoid the wire heating up
and causing burns if touched. If the current rises too high, reduce the voltage using
the variable power supply.
● If the wire is taut, safety goggles should be worn in case it snaps.
● The wire heating up might additionally cause the resistance of the wire to change,
affecting measurements. To reduce this, disconnect it in between measurements or
reduce the voltage of the supply so the current is lower.
● The wire should be free from kinks and held straight so the measurement of the
length is as accurate as possible.
What is the equipment needed to investigate the electrical characteristics for a ohmic and non-ohmic components
● Ammeter
● Voltmeter
● Variable resistor
● Copper block
● Filament lamp
● Diode
● Power Pack
● Wires
What is the method needed to investigate the electrical characteristics for a ohmic and non-ohmic components
- Set up the circuit as shown where ‘component’ is the
filament lamp, copper block or diode. - Vary the voltage across the component by changing the
resistance of the variable resistor, using a wide range of
voltages. - For each voltage record the current 3 times and
calculate the mean current. - Make sure to switch off the circuit in between readings to prevent heating of
components. - Repeat for all 3 components.
What is the calculation needed to investigate the electrical characteristics for a ohmic and non-ohmic components
● Plot a graph of mean current against voltage (an I-V characteristic graph) for each
component.
● Compare the shapes of each graph and consider the reasons behind the difference
between the filament lamp and copper block characteristic graph.
What is the safety needed to investigate the electrical characteristics for a ohmic and non-ohmic components
● The components will get hot especially at higher voltages so be careful when
handling them and disconnect the power supply in between readings.
● Do not put non-insulated metal into the plug sockets to reduce the risk of
electrocution.
● The voltmeter will not have infinite resistance and the ammeter will not have 0
resistance (ie. they won’t be ideal) therefore the voltages and currents displayed may
be slightly inaccurate.
● The equipment used (except from the components) and the temperature of the area
should be controlled as these can affect the results.
● To reduce uncertainty take more readings at more voltages and use ammeters and
voltmeters with greater resolution.
What equipment is needed to find the internal resistance of a cell
● Battery or cell
● Voltmeter
● Ammeter
● Variable resistor
● Switch
What method is needed to find the internal resistance of a cell
- Connect a variable resistor, switch, ammeter, battery in series and voltmeter in parallel.
- Set the variable resistor to its maximum value.
- Close the switch and record voltage from the voltmeter
and the current from the ammeter, open the switch
between readings to prevent heating of the variable
resistor. - Decrease the resistance of the variable resistor and
repeat this, obtaining pairs of readings of V and I over the
widest possible range.
What calculations is needed to find the internal resistance of a cell
● ε = I(R + r) = V + Ir ⇒ V = −rI + ε , this is in the form y=mx+c (a straight line graph)
● Plot a graph of V against I and draw a line of best fit. The y-intercept will be the emf
and the gradient will be the negative internal resistance.
What safety and improvements is needed to find the internal resistance of a cell
● Another resistor can be included in series with the other to avoid high currents which
could be dangerous and make the wires and variable resistor get hot.
● Only close the switch for as long as it takes to take each pair of readings. This will
prevent the internal resistance of the battery or cell from changing during the
experiment.
● Use fairly new batteries/cells because the emf and internal resistance of run down
batteries can vary during the experiment.
● Check there is no systematic error from the ammeter and voltmeter by calibrating
them beforehand.
What is the equipment needed to find the maximum power of a cell
● Battery
● Ammeter
● Voltmeter
● Variable resistor
What is the method needed to find the maximum power of a cell
Record the terminal voltage (reading on the voltmeter) for
at least 8 different current values determined by altering
the variable resistor, the range should be quite wide in
order to see the trend in results clearly.
What is the calculations needed to find the maximum power of a cell
Calculate the power supplied by the battery for each current value by using P = VI
and also calculate the resistance at each current value by R = V/I. The headings for
the table your results and calculations should be recorded in are illustrated below: Current, Voltage, Power, Resistance
What is the safety needed to find the maximum power of a cell
Do not use too high a voltage as the components can become too hot, be damaged
and the risk of electrocution is greater.
What is the equipment needed to find the combination of resistors
● Multiple resistors of different known resistances
● Ohmmeter/multimeter
● Crocodile clips
● Voltmeters
● 5 V power supply
● Leads
What is the method needed to find the combination of resistors
- Check the given resistance of the resistors is accurate by clipping one to some crocodile
clips and connecting these to an ohmmeter which will display the actual resistance of the
resistor allowing calculations to be more accurate. - Design at least 3 circuits such as the two shown below. Connect voltmeters across the
resistors of known resistance as shown:
The cells in the example circuits shown are all 5 V. - Calculate the theoretical total resistance of each circuit designed:
○ For circuit 1 (left) the resistance is 5 + the combined resistance of the parallel
resistors (RC) 1/RC= ⅓ + ⅙ = ½ so RC=2 Ω hence the total R = 7 Ω
○ For circuit 2 (middle) the resistors are in series so the combined resistance is 8
+4.5+6 = 18.5 Ω
○ For circuit 3 (right) all the resistors are in parallel so 1/RT
= 1/3 + 1/5 + 1/7
1/RT=71/105 RT=105/71 = 1.48 Ω (3sf) - Next, record the voltage on each voltmeter and find this voltage as a percentage of the 5 V
supply. - Find the resistance of each resistor as a percentage of the total resistance of its circuit.
- Compare the corresponding voltmeter percentages and resistor percentages.
- You should find that they are approximately equal, this is because the voltage across a
resistor is proportional to its resistance, ie. the resistor with ¾ of the resistance will have ¾
of the available p.d across it
What is the safety and notes needed to find the combination of resistors
● Using a 5 V power supply minimizes risk of electrocution and components becoming too
hot.
● Calibrate the voltmeters before connecting them to avoid systematic error
What is the equipment needed for circuits with more than one source of e.m.f
● Cells
● Leads
● Voltmeter
● Resistor
What is the methods needed for circuits with more than one source of e.m.f
- Set up the first circuit as shown in the diagram to the right, the cells do
not have to be 5 V. - Record the voltage across the resistor, as the resistor is the only
component this will be the potential difference supplied by the cells
(with some error due to internal resistance). - Set up the second circuit as shown in the diagram below the first, once
again record the current across the resistor. - Swap at least one of the cells in the series circuit so that they are of
different voltages and record the reading on the voltmeter again.
What is the calculations needed for circuits with more than one source of e.m.f
● Calculate the expected combined potential difference for each cell
combination using the rules about cells in series and parallel.
○ The combined potential difference for cells in series will be the
sum of their individual voltages (VTOT= V1
+ V2 + … Vn)○ 2 cells of the same voltage connected in parallel will have an
overall potential difference of that same voltage. This is
because their terminals are electrically at the same point so
the potential between these two points is the same, however
batteries connected in parallel have a longer lifetime than
those connected alone.
● Compare the theoretical combined potential difference and compare it to the actual, discuss
the reasons behind this difference e.g internal resistance
What is the safety needed for circuits with more than one source of e.m.f
● Do not connect 2 cells of different voltage in parallel, particularly if the difference is large. 2
cells of different voltage connected in parallel will not remain at different voltages as the one
of higher voltage will discharge into the one of lower until they are equal which can cause
wires to be burnt, sparks when connecting the cells, overheating and failure of both
batteries.
● Do not use high voltage batteries to minimise risk from electrocution.
● The resistor may get hot so touch it with caution.
● The internal resistance of the cells will affect the reading on the voltmeter, adding a switch
to the circuit, leaving it open and connecting a voltmeter across the cells would allow for a
more accurate determination of their combined emf.
What is the equipment needed for using non-ohmic devices as sensors
● Cell
● LDR
● Thermistor
● Resistor
● Leads
● Voltmeter
● Lamp with dimmer switch
● Digital light sensor
● Ice
● Kettle
● Thermometer
● Beaker
What is the method needed for using non-ohmic devices as sensors
Connect a battery, LED, resistor and voltmeter.
Make the area surrounding the circuit as dark as possible,
record the value of this light intensity using the digital light
sensor.
3. Record the voltage across the resistor for this light intensity.
4. Using the lamp with a dimmer switch increase the light
intensity slightly and record the new value recorded by the
sensor and record the voltage across the resistor.
5. Repeat this process until the light intensity cannot be
increased any further.
What is the calculations needed for using non-ohmic devices as sensors
● Plot a graph of voltage across the resistor against light intensity and draw a line of
best fit.
● This can be used as a calibration curve.
● Move the circuit to an area of unknown light intensity and record the voltage across
the resistor.
● Using the calibration curve, find the corresponding light intensity to this voltage.
What is the safety needed for using non-ohmic devices as sensors
● Be careful not to be scalded by boiling water by not letting it splash.
● Do not look directly into the lamp.
● Be careful not to trip when the room is dark.
● To increase the accuracy of the calibration curve, take as many readings as possible
over a wide range so that there are as many data points as possible.
● The resistance of the LDR and thermistor decreases with the increase in light
intensity and temperature respectively.
● Ohm’s law is that the current between two points is directly proportional to the
potential difference across those points, as R=V/I this means the resistance between
those points is constant, a non-ohmic device doesn’t obey ohm’s law.
● The potential difference provided by the cell is shared between the resistor and the
non-ohmic (changes resistance) devices. A greater proportion of the voltage is
shared across the resistor as the resistance of the non-ohmic device decreases.
What is the equipment needed to determine the wavelength of light using a diffraction grating
● Diffraction grating
● Laser
● Screen
● Ruler
What is the method needed to determine the wavelength of light using a diffraction grating
- Shine the laser through the diffraction grating onto the screen.
- Measure the distance between the central fringe and the one beside it (1st order -
see below). - Measure the distance between the grating and the screen.
What is the calculations needed to determine the wavelength of light using a diffraction grating
● The formula associated with diffraction gratings is d sinθ λ. = n
Where d is the distance between the slits, θ is the angle to the normal made by the
maximum, n is the order and λ is the wavelength.
● To find tan θ divide the distance between the central fringe and the one beside it by
the distance between the grating and the screen (tanθ=opp/adj) then use inverse tan
( θ) to find θ. tan−1
● To find d read the information on the packaging, it will say how many lines per mm.
Note that if it has 350 lines/mm that is 350,000 lines/m and 1/350,000 is the slit
spacing.
● We measured the distance to the first order hence n = 1.
● Substitute all these values into dsinθλ = (n is not included as n = 1) to find the
wavelength of the laser.
What is the safety needed to determine the wavelength of light using a diffraction grating
● Also calculate the wavelength using 2nd and 3rd order measurements and find the
average of these values for the mean wavelength.
● Vary different properties such as the number of lines in the diffraction grating and the
wavelength of the light to see how they affect θ.
What is the equipment for
Determining the speed of sound in air by formation of
stationary waves in a resonance tube
● Tuning fork
● Hammer for tuning fork
● Resonance tube (open at one end)
● Water reservoir
What is the method for
Determining the speed of sound in air by formation of stationary waves in a resonance tube
- Fill the resonance tube halfway with water.
- Hit the tuning fork of a known frequency with a hammer and hold it above the tube
then lower the water level until the intensity of sound is amplified, when resonance
(loudest sound) is heard, mark the water level with a rubber band. - Then, lower the water further until the next point of resonance is heard and mark it,
keep going in this manner as far as possible.
Resonance occurs when the open tube length is λ/4, 3λ/4 and 5λ/4.
What is the calculations for
Determining the speed of sound in air by formation of stationary waves in a resonance tube
● Using the length from the top of the tube to the rubber bands, find the wavelength,
e.g. if the first maximum is 15cm down the tube, the wavelength is 15 x 4 = 60cm (0.6
m) repeat this step for each of the maxima and then calculate the mean wavelength.
● Multiply the mean wavelength (m) by the known frequency (Hz) to find the speed of
the sound wave in m/s for the temperature of the room at that time.
What is the safety for
Determining the speed of sound in air by formation of stationary waves in a resonance tube
● Don’t let the tuning fork touch the resonance tube as the vibrations can break the tube.
● The open end acts as an antinode, but the real antinode is about 0.6 r from the end (r
is the tube radius). This correction can be added to get a more accurate value when
only amplified sound (resonant point) can be measured.
● Using a resonance tube with a scale on it will help account for error when measuring
the length of a curve tube with a ruler.
What is the equipment needed to determine the frequency and amplitude of a wave
● Oscilloscope
● Leads
● Microphone
● Loudspeaker
● Musical Instrument
What is the method needed to determine the frequency and amplitude of a wave
- Connect the microphone to the oscilloscope input and play one note on the musical
instrument into the microphone. - Use the oscilloscope to determine both the frequency and amplitude of the signal
(see how to do this below). - Compare these frequency and amplitude values to database values to determine the
note played on the instrument and whether it is in tune.
What equipment is needed to determine planks constant
● Light emitting diodes of varying colours
● Ammeter
● Voltmeter
● Leads
● Cell
● Resistor
What method is needed to determine planks constant
Connect a battery, ammeter LED and voltmeter with a potentiometer
2. Find the wavelength of light the LED is emitting,
this will either be on the packaging or you can find it
online depending on the colour of the LED.
3. Find the threshold voltage of the LED by recording
the potential difference across it at which it lights
up/current is shown to be flowing by the ammeter.
4. Find the threshold voltage for a range of LEDs of different wavelengths and record these in
a table of wavelength against threshold voltage.
What calculations is needed to determine planks constant
● Plot a graph of threshold voltage (V) against 1/wavelength (1/λ) and calculate the gradient.
The energy of the photons emitted by the LED have energy (E) equal to:
E = hf = hc/λ they also have energy E = eV where e is the charge on an electron and V is
the potential difference applied, we can equate these to get:
eV = hc/λ
Multiply both sides by λ and divide both sides by e to find:
Vλ = hc/e
Vλ is the gradient (m) of the graph so planck’s constant (h) can be found by calculating the
product of gradient and e/c (where e is the charge on an electron and c is the speed of light
in a vacuum).
What notes is needed to determine planks constant
● Use a wide range of wavelength LEDs and take repeats to draw the most accurate line of
best fit.
● Make sure the wavelength is in metres and the voltage is in volts.
What equipment is needed to do experiment with light
● Microwave oven
● Ruler
● Chocolate bar
What method is needed to do experiment with light
- Remove the turntable wheels from the microwave so that the plate is stationary.
- Place the chocolate on the turntable and turn the microwave on for 30 seconds.
- Take the chocolate out and observe the pattern of melted and solid strips.
- Using the ruler, measure the distance between 4 melted strips and divide by 3 to find
the distance between adjacent melted strips.
What calculations is needed to do experiment with light
● The microwaves in the oven reflect
off the walls and interfere to form
standing waves with nodes and
antinodes, the antinodes are where
the chocolate melts as the wave is
at maximum amplitude. The nodes
are where it stays solid, as these are
the points of minimum displacement.
● The distance between 2 adjacent melted strips is the distance between 2 antinodes,
however this is only half a wavelength
● Multiply the distance between the 2 adjacent strips by 2 to find the wavelength of the
microwaves, make sure this value is in m.
● The frequency of the microwaves is shown on the microwave oven, make sure this
value is in Hz.
● Multiply the frequency by the wavelength to find the speed of microwaves as c = fλ.
What safety is needed to do experiment with light
● EM waves will travel slightly slower in air than in a vacuum, the speed of light in air is
299,700,000m/s whereas it is 299,792,458m/s in a vacuum.
● Using a longer bar of chocolate reduces the uncertainty in the measurements and
using one of uniform thickness makes it easier to discern where the antinodes are (as
the thinner parts will melt faster in a non-uniform bar).
● Microwaves can cause burns, make sure the protective mesh in the inner screen is
present.
What equipment is Investigating refraction and total internal reflection of light using ray boxes, including
transparent rectangular and semi-circular blocks
● Ray box
● Semi circular pyrex/glass block
● Rectangular pyrex/glass block
● White paper sheets with protractor printed on
● Plain white paper
● Pencil and ruler
What method is Investigating refraction and total internal reflection of light using ray boxes, including
transparent rectangular and semi-circular blocks
(semi-circular block)
1. To investigate refraction, place the semi-circular block on top of the protractor with
the centre of its diameter aligned with 0° on the protractor.
2. Direct the ray towards this 0° point from a point at nearly 180° and using the pencil
and ruler trace the ray entering the block and leaving.
3. Repeat this, moving the ray around every 10°.
4. Record the angle at which the angle of refraction is 90°, (the ray leaves along the
straight boundary of the block). This is the critical angle.
5. Increase the angle further and observe that it does not leave the block, it is being
totally internally reflected.
(rectangular block)
1. Place the block on white paper and draw in pencil around it to mark its position
2. Mark a point on the longer edge approximately 1-2 cm from the
corner, this is the target for the incident ray.
3. Aim the beam normal to the block and trace the entry and exit
ray, the straight part of the protractor should be against the
long side of the block.
4. Rotate the beam 10° each time, still entering the block at the same marking and
record each path.
5. For each position, measure the angle of incidence (angle between the incident ray
and normal) and the angle of refraction (angle between the refracted ray and
normal).
What calculations is Investigating refraction and total internal reflection of light using ray boxes, including
transparent rectangular and semi-circular blocks
● The refractive index of the rectangular block, where i is the angle of n = sin i/sin r
incidence and r is the angle of refraction. To derive this formula replace n1
in Snell’s
law with 1 as this is the refractive index of air.
● The refractive index of the semi circular block is found by, where c is the n = 1/sin c
What notes is Investigating refraction and total internal reflection of light using ray boxes, including
transparent rectangular and semi-circular blocks
● The printed protractor will have a large error and a real protractor underneath tracing
paper may give more accurate results.
● Using a laser gives more defined rays so there is less uncertainty about where to
trace the line (as the light is monochromatic so all light rays are refracted by the
same amount).
● Do not shine the light from the ray box in eyes as it can damage the retina.
● Lasers can permanently damage your eyesight therefore, when using lasers there
are several safety precautions, which must be followed:
○ Wear laser safety goggles
○ Don’t shine the laser at reflective surfaces
○ Display a warning sign
○ Never shine the laser at a person
Young’s Double Slit Experiment Equipment
● Laser
● Double slit
● Screen
● Ruler
Young’s Double Slit Experiment method
- Shine the laser through the double slit so each slit acts as coherent point source.
- Observe the pattern of light and dark bands on the screen, mark the centre of each bright
spot then turn the laser off and measure the distance of at least 4 fringe spacings. - Measure the distance from the slits to the screen (D) and record the distance between the
slits, s (should be given by manufacturer)
Young’s Double Slit Experiment calculations
● Find the fringe spacing by dividing the distance across 4 adjacent fringes by 3 to find
fringe spacing (w).
● Rearrange the double slit equation to make 𝜆 the subject, 𝜆= ws/D , and substitute the
other values, making sure all units are in m, to calculate wavelength.
Young’s Double Slit Experiment Saftey
● Lasers can permanently damage your eyesight therefore, when using lasers there
are several safety precautions, which must be followed:
○ Wear laser safety goggles
○ Don’t shine the laser at reflective surfaces
○ Display a warning sign
○ Never shine the laser at a person
● Vary wavelength by changing the colour of the laser and see how this affects the
fringe spacing, varying different values can show how they are related.
● Use white light to see a less intense diffraction pattern with a bright white central
fringe and spectral adjacent fringes
Equipment for observing polarizing effects using microwaves and light
● Polarising filters
● Metal grilles
● Microwave detector
● Microwave transmitter
method for observing polarizing effects using microwaves and light
- For light, hold a polarising filter up to eye level, place another filter behind it and
rotate it to observe that when the filters are perpendicular, no light gets through. - For microwaves, place a vertically aligned metal grille in front of the transmitter
(which transmits vertically plane polarised waves) and the detector behind the grille. - To make sure the detector is working and the waves are vertically aligned turn on the
transmitter and check the detector receives the waves with and without the grille. - Place a horizontally aligned grille behind the first and observe whether the detector
records any microwaves.
safety for observing polarizing effects using microwaves and light
● Microwaves can cause burns if their intensity is too high, do not stand in front of the
transmitter when it is on.
● Do not look directly into a bright light as it damages eyesight.
● Only transverse waves can be polarised.
● Reflected light is partially polarised as the light perpendicular to the surface is flipped
round when reflected, and destructively interferes with itself, hence polaroid
sunglasses reduce glare by blocking light polarised in this orientation.
Equipment for observing the random nature of radioactive decay
● Radioactive source (with a short half-life, e.g. protactinium)
● Geiger-muller tube (connected to a counter)
● Clamp stand
● Long-handled tongs for handling the source
● Source holder
● Metre ruler
method for observing the random nature of radioactive decay
- Set up the clamp stand and attach the GM tube to it, making sure to keep the GM tube
connected to the counter. - Before moving the radioactive source into the room you will be working in, you must calculate
the background count by switching on the counter (connected to the GM tube) for at least 30
seconds. Record this background count. - Remove the radioactive source from its storage box using long-handled tongs and place it 0.1 m
away from the GM tube in the source holder. - Switch on the counter and take readings of count for 10 seconds every 30 seconds for 5
minutes. When recording readings, you should subtract the background count from the
recorded value to produce a corrected count rate. - Repeat this procedure twice more with a new source, after waiting for at least 5 minutes
between repeats, and find the average count for each reading.
calculations for observing the random nature of radioactive decay
● Draw a table of corrected count rate against time, where corrected count is the difference
between measured count rate and background count (making sure the units of count rate are
the same).
● Plot a graph of corrected count rate against time and draw a line of best fit, which in this case
will be a curve.
● You will be able to see that the decay is exponential. The time taken for the corrected count to
halve should be constant and the name for this value is the half-life (T1/2) of the sample.
● Using your curve you can measure the half-life of the radioactive substance by measuring the
time taken for the count rate to halve, across several half-lives (if possible) and finding a mean.
safety for observing the random nature of radioactive decay
Ionising radiation can be incredibly dangerous, so to reduce your exposure:
○ Never directly handle the source, use long-handled tongs
○ Store the source in a lead-lined container when not in use
○ Never point the source at others
○ Keep the source as far away as possible from yourself and others
Even though the decay of the radioactive substance can be seen to follow an exponential
decay, the process of nuclear decay is completely random. This can be seen from your
measured values of count rate and from the fact that your graph (probably) won’t follow a
perfect exponential decay curve.
Equipment for Investigating the absorption of α-particles,
β-particles and γ-rays by appropriate materials
● 3 unlabelled radioactive sources e.g. Americium-241, Strontium-90, Iodine-131
● A few sheets of paper
● 1 cm aluminium
● 4 cm lead
● Geiger counter
● Long handled tongs for handling sources
method for Investigating the absorption of α-particles,
β-particles and γ-rays by appropriate materials
- Before moving the radioactive source into the room you will be working in, you must
calculate the background count by switching on the counter (connected to the GM
tube) for at least 5 minutes. Record this background count. - Using the tongs place the source about 5 cm from the geiger counter, and measure
the count rate after 5 minutes. Calculate the corrected count rate. (Corrected count
rate is the difference between measured count rate and background count). - Place a few sheets of paper in front of the source and repeat the step above.
- If the corrected count rate drops to 0 we can assume the source was emitting only
alpha radiation, if there is a significant drop we can assume it was emitting partly
alpha radiation. - Repeat the above step using the aluminium foil and 4 cm of lead. If there is a
significant decrease in count rate for aluminium foil, then beta radiation is being
emitted and if there is a significant decrease in count rate for the lead block, then
gamma radiation is being emitted. - Repeat this procedure for each of the sources to identify the types of radiation they’re
emitting.
Safety method for Investigating the absorption of α-particles,
β-particles and γ-rays by appropriate materials
● Ionising radiation can be incredibly dangerous, to reduce your exposure:
○ Never directly handle the source, use long handled tongs
○ Store the source in a lead-lined container when not in use
○ Never point the source at others
○ Keep the source as far away as possible from yourself and others
Equipment for Estimate a value for absolute zero from gas pressure
and volume from volume
● Thermometer
● Large beaker
● Kettle
● Capillary tube sealed at one end, containing a sample of air trapped by a small amount of
sulphuric acid
● 30 cm ruler
● Elastic bands
● Cold water/ice
methods for Estimate a value for absolute zero from gas pressure
and volume from volume
- Attach the 30 cm ruler to the capillary tubes using 2 elastic bands so that the 0 cm mark is
at the very start of the length of the air sample. - Boil water using the kettle, leaving it to cool slightly before pouring it into the large beaker.
- Place the capillary tube (attached to the ruler) into the beaker, with the open end facing
upwards. - Measure the temperature of the water using the thermometer, making sure to stir the water
with the thermometer beforehand, and record this value. - Measure the length of the air sample without removing the capillary tube from the beaker.
- Decrease the temperature of the water by 5 °C by adding a small amount of cold water/ice
to the beaker, and again measure the temperature and length of the air sample. - Repeat the above step until the water reaches room temperature.
calculations for Estimate a value for absolute zero from gas pressure
and volume from volume
● Draw a graph of length against temperature and draw a line of best fit.
● The line of best fit will have the equation y = mx+c (as it is a straight line), where y is the
length (l) and x is the temperature (θ):
l = mθ + c
● m is the gradient of the line of best fit which can be calculated by finding the change in l
over the change in θ, over a large interval.
● c is the y-intercept of the graph which can be calculated by using two points from the line of
best fit and substituting them into the equation of the line of best fit (above).
● At absolute zero the volume of the air sample will be 0, therefore its length (l) will also be
zero. Substitute this result (and your known values of m and c) into the equation of the line
of best fit to calculate absolute zero.
Absolute zero = -c/m
safety for Estimate a value for absolute zero from gas pressure
and volume from volume
● Sulphuric acid is corrosive therefore may cause irritation to skin and damage to eyes so
safety goggles must be worn and the capillary tube must be handled carefully.
● Boiling water may cause burns so care should be taken when handling it.
equipment for Estimate a value for absolute zero from gas pressure
and volume from pressure
● Thermometer
● Bourdon gauge
● Flask
● Beaker large enough to fully contain the flask
● Bung with connective tubing which attaches to the bourdon gauge
● Kettle
● Cold water/ice
method for Estimate a value for absolute zero from gas pressure
and volume from pressure
- Place the bung into the neck of the flask making sure that it sits in the flask tightly so that it
does not fall out. Attach the connective tubing to the bourdon gauge, again making sure it
fits the gauge tightly. - Place the flask into the large beaker.
- Boil water using the kettle, leaving it to cool slightly before pouring it into the large beaker
until it reaches the bung in the flask. - Measure the temperature of the water using the thermometer, making sure to stir the water
with the thermometer beforehand, and record this value. - Record the value of pressure on the bourdon gauge.
- Decrease the temperature of the water by 5 °C by adding a small amount of cold water/ice
to the beaker, and again measure the temperature and pressure of the air in the flask. - Repeat the above step until the water reaches room temperature.
calculations for Estimate a value for absolute zero from gas pressure
and volume from pressure
● Draw a graph of pressure against temperature and draw a line of best fit.
● The line of best fit will have the equation y = mx+c (as it is a straight line), where y is the
pressure (p) and x is the temperature (θ):
p = mθ + c
● m is the gradient of the line of best fit which can be calculated by finding the change in p
over the change in θ, over a large interval.
● c is the y-intercept of the graph which can be calculated by using two points from the line of
best fit and substituting them into the equation of the line of best fit (above).
● At absolute zero the pressure of the air sample will be 0. You can substitute this result (and
your known values of m and c) into the equation of the line of best fit to calculate absolute
zero.
Absolute zero = -c/m
safety for Estimate a value for absolute zero from gas pressure
and volume from pressure
● Boiling water may cause burns so care should be taken when handling it.
● Take care when using glassware. If a breakage occurs avoid touching any shards of glass
with bare skin, and inform a teacher.
Equipment Investigating the relationship between pressure and
volume.
● Clamp stand
● 100 g masses and a mass holder
● String
● Syringe
● Tubing which fits tightly on the nozzle of the syringe
● Pinch clip
● Vernier calipers
methods Investigating the relationship between pressure and
volume.
- Take the plunger out of the syringe. Measure the syringe’s internal diameter using vernier
calipers and record this value. - Place the plunger back into the syringe and draw in 5 cm3
of air. - Without moving the plunger at all, place the tubing over the nozzle of the syringe and pinch
it shut using the pinch clip. Make sure that the pinch clip is as close to the nozzle as
possible. - Set up the clamp stand and attach the syringe to it so that the plunger is pointing
downwards, leaving quite a bit of space below the syringe. - Attach the string to the end of the plunger, leaving a loop. Then, attach the 100 g mass
holder to this loop. - Record the volume recorded by the syringe.
- Add a 100 g mass to the holder and record the volume.
- Repeat the above step until the total mass is 1000 g.
- Repeat the whole procedure twice more and calculate the mean values of volume.
calculations Investigating the relationship between pressure and
volume.
● Calculate the cross-sectional area of the syringe in metres using the following equation:
A = πd^2 / 4
● Calculate the force exerted by each of the recorded masses by calculating their weight:
Weight = m × g
Where m is the mass and g is the gravitational field strength, 9.81 Nkg-1
.
● Using the equation P = F/A, calculate the total pressure exerted on the gas at each value of
force exerted.
● Total pressure is the sum of the pressure of the air sample and atmospheric pressure,
therefore to find the pressure of the air sample you must subtract the atmospheric pressure
(101 kPa) from your calculated values.
● Plot a graph of 1/V against the pressure of the air sample and draw a line of best fit.
notes Investigating the relationship between pressure and
volume.
● Your line of best fit should form a straight line through the origin showing that 1/V and the
pressure of the air sample are directly proportional or, that V and the pressure of the air
sample are inversely proportional.
Equipment Estimating the work done by a gas as its temperature increases
● Thermometer
● Large beaker
● Kettle
● Capillary tube sealed at one end, containing a sample of air trapped by a small amount of
sulphuric acid (at atmospheric pressure)
● 30 cm ruler
● Elastic bands
● Cold water/ice
● Vernier calipers
methods Estimating the work done by a gas as its temperature increases
- Measure the internal diameter of the capillary tube using vernier calipers.
- Attach the 30 cm ruler to the capillary tubes using 2 elastic bands so that the 0 cm mark is
at the very start of the length of the air sample. - Boil water using the kettle, leaving it to cool slightly before pouring it into the large beaker.
- Place the capillary tube (attached to the ruler) into the beaker, with the open end facing
upwards. - Measure the temperature of the water using the thermometer, making sure to stir the water
with the thermometer beforehand, and record this value. - Measure the length of the air sample without removing the capillary tube from the beaker.
- Decrease the temperature of the water by 5 °C by adding a small amount of cold water/ice
to the beaker, and again measure the temperature and length of the air sample. - Repeat the above step until the water reaches room temperature.
calculations Estimating the work done by a gas as its temperature increases
● Calculate the cross-sectional area of the capillary tube, using the following equation:
A = πd^2 / 4
● Calculate the volume of the air sample at each length by multiplying each length by the
cross-sectional area.
● Plot a graph of volume against temperature and draw a line of best fit.
● Your line of best fit should be a straight line, meaning that volume and temperature are
directly proportional.
● The air inside the capillary tube is allowed to expand freely within the tube meaning it is
under atmospheric pressure. As the pressure of the air sample is constant, you can use the
following equation to calculate the work done:
Work done = pΔV Where p in this case is atmospheric pressure (101 kPa) and is the change in volume. V Δ
● As temperature and volume are directly proportional (as shown by your graph), you can see
that as temperature increases, the work done on the gas also increases.
safety Estimating the work done by a gas as its temperature increases
● Sulphuric acid is corrosive therefore may cause irritation to skin and damage to eyes so
safety goggles must be worn and the capillary tube must be handled carefully.
● Boiling water may cause burns so care should be taken when handling it.
Equipment Investigating capacitors in series and parallel combinations using ammeters and voltmeters
● Capacitors x 2
● Cell
● Voltmeter
● Ammeter
● Switch
● Variable resistor
● Stopwatch
method Investigating capacitors in series and parallel combinations using ammeters and voltmeters
● Set up the circuit as shown to charge the capacitor which is
represented by the 2 parallel lines of equal length.
● Closing the switch allows current to flow, adjust the variable
resistor to keep the current constant for as long as possible.
● Record the value of the constant current as well as the
potential difference and the time since closing the switch in a
table.
calculation Investigating capacitors in series and parallel combinations using ammeters and voltmeters
● To calculate the charge (C) across the capacitor, multiply the fixed charging current (A)
value by the time in seconds since the switch was closed.
● Plot a graph of charge (C) against voltage (V) and draw a line of best
fit.
● Find the gradient of the line of best fit, this is the capacitance of the
capacitor in farads.
Equipment, investigating the factors affecting capacitance
● Clamp stand
● Leads
● Multimeter
● Large aluminium plates
● Two small wooden blocks and one large wooden block
● Crocodile clips
● Metre ruler
methods, investigating the factors affecting capacitance
- Set up the clamp stand and attach one of the aluminium plates to it, using the wooden
blocks to insulate the aluminium plate as shown in the diagram below. Make sure the plate
is parallel to the work bench. - Next, place the large wooden block below the aluminium plate and place the second plate
on it, making sure both plates are perfectly aligned. You can do this by using a metre ruler
to check the edges of the plates are in the same place. - Using the metre ruler, make sure the distance between the two plates (d) is 10 cm, and
make sure this is kept constant throughout the experiment. - Measure the length and width by which the aluminium plates overlap using the metre ruler.
- Using the crocodile clips and leads connect the two plates to a multimeter and record the
capacitance. - Disconnect the circuit and move the large wooden block and the plate on top of it, to the
right by 5 cm, making sure that the entire width of the plates still overlap. - Measure the new length by which the plates
overlap, reconnect the circuit and measure the
capacitance. - Repeat the last two steps until you have at least
7 readings. - Repeat the entire procedure twice more and find
mean values of capacitance for each reading
calculations, investigating the factors affecting capacitance
● Find the area of overlap by multiplying each length by the width of the plates.
● Plot a graph of capacitance against the area of overlap (at each length of overlap), and
draw a line of best fit.
● Your line of best fit should be a straight line passing through the origin, which shows that
capacitance and area are directly proportional, as shown by the capacitance equation:
C = A εrε0 / d
Where A is the area of overlap, ε0
is the permittivity of free space, εr
is the relative permittivity and d
is the distance between the plates.
● Your line of best fit will have the equation y = mx, where y is the capacitance and x is the
area, meaning that its gradient will be equal to following the equation above (as the d
ε0
relative permittivity of air is 1).
● Therefore, you can find the value of ε0
by multiplying the gradient of your line of best fit by
the distance between the plates.
notes, investigating the factors affecting capacitance
● If your line of best fit does not pass through the origin this may be because of a zero error
caused by an uncalibrated multimeter or stray capacitance.
● You can investigate other factors by varying what is changed and what is kept constant in
the procedure:
➔ To investigate the distance between the plates (d) - vary d, and keep the area of
overlap constant.
➔ To investigate the relative permittivity between the plates (εr
) - vary the insulator
placed between the two plates whilst keeping the area of overlap and distance
between the plates constant.
Equipment of SMH on simple pendulum
● String
● Small, dense ball bearing (to act as the pendulum bob)
● Clamp stand
● Metre ruler
● Stopwatch
● Fiducial marker (e.g pin and blu-tack)
method of SMH on simple pendulum
- Attach the ball bearing to the string and attach this to the clamp stand as shown in the
diagram below. - Adjust the length l, which is from where the string is attached to the clamp stand to the
center of the ball bearing, until it is 1.0 m using the metre ruler. - Wait until the pendulum bob stops moving completely, then place the fiducial marker
directly underneath the bob. This represents the centre of oscillations and will make it
easier to count how many oscillations the pendulum has undergone. - Pull the pendulum bob to the side slightly and let it go so that it is oscillating with a small
amplitude and in a straight line. - As the pendulum passes the fiducial marker, start the stopwatch and count the time taken
for it to complete 10 full oscillations. - Take two more readings of the time period for 10 oscillations and calculate a mean.
- Reduce the length l by 10 cm and repeat the last 3 steps of the procedure.
- Repeat the last step until the length l is 0.2 m.
calculations of SMH on simple pendulum
● Divide the mean values of time period at each length by 10 to get the time period for a
single oscillation (T).
● Draw a table of the values of T^2
against l. Use your table to plot a graph of T^2
against l, and
draw a line of best fit
Your line of best fit should be a straight line through the origin, showing that l is directly
proportional to T^2
.
notes of SMH on simple pendulum
● Using a fiducial marker and timing over several oscillations (as directed) will reduce the
uncertainty in your measurements.
● Repeating measurements and finding a mean will reduce the effect of random errors.
● To reduce the uncertainty further you could use light gates attached to a data logger to
record the period of 10 oscillations.
● The angle by which you pull the pendulum bob to start it oscillating must be less than 10°,
otherwise it will not undergo SHM.
● If you are unaware of the relationship between length and time period, you can plot a graph
of log10 T against log10 l.
method of SMH on Mass-spring system
- Attach the spring to the clamp stand and attach the mass holder to the spring as shown in
the diagram below. - Wait until the spring stops moving completely, then place the fiducial marker at the very
bottom of the mass holder, using the metre ruler to align it perfectly. This represents the
centre of oscillations and will make it easier to count how many oscillations the mass-spring
system has undergone. - Pull the spring down slightly and let it go so that it is oscillating with a small amplitude and
in a straight line. - As the bottom of the mass holder passes the fiducial marker, start the stopwatch and count
the time taken for it to complete 10 full oscillations. - Take two more readings of the time period for 10 oscillations and calculate a mean.
- Add a 100 g mass to the mass holder and repeat the last 3 steps of the procedure.
- Repeat the last step until the total mass is 800 g (including the mass holder which is 100 g).
Equipment Damped oscillations
● Clamp stand
● Two 15 cm rulers
● Spring
● 100 g masses
● 500 g mass holder
● 400 g mass holder
● Stopwatch
● Fiducial marker (e.g pin and blu-tack)
● Damping card (circular cards with a hole in the centre which is smaller than a 100 g mass
but larger than the stem of the mass holder so it can be wedged between two masses to
hold it in place)
● Rubber bands
methods Damped oscillations
- Attach the spring to the clamp stand and attach the 500 g mass holder to the spring as
shown in the diagram below. - Wait until the spring stops moving completely, then place the fiducial marker at the very
bottom of the mass holder. This represents the centre of oscillations and will make it easier
to count how many oscillations the mass-spring system has undergone. - Attach the 15 cm ruler, either side of the fiducial marker, using rubber bands. These will be
used to measure the amplitude of the oscillations. - Pull the spring down slightly and let it go so that it is oscillating with a small amplitude and
in a straight line. - As the bottom of the mass holder passes the fiducial marker, start the stopwatch and count
the time taken for it to complete 10 full oscillations. - Once again, pull down the spring and let it go, allowing it to oscillate with a small amplitude
and in a straight line. Remember to record the amplitude that the spring is pulled to, as this
will be the maximum amplitude at the start of the first oscillation. - Measure the maximum amplitude of the spring at the start of every oscillation for at least 10
oscillations. - Repeat the above two steps twice and calculate the mean values of maximum amplitude at
each oscillation. - Repeat the above procedure but this time using the 400 g mass holder and the damping
card wedged between the mass holder and a 100 g mass.
calculations Damped oscillations
● Divide the collected values of time period by 10 to get the time period for a single oscillation
(T).
● Calculate the frequency of the oscillations by using the equation below, when the damping
card is present and when it is not.
f =1/T
● Plot a graph of the maximum amplitude against the number of oscillations for both systems
and draw a line of best fit, which in this instance is an exponential decay curve.
safety Damped oscillations
● Be careful when handling the masses. Dropping them may cause injury.
● If the clamp stand is unstable, a counterweight placed on the base of the clamp stand can
be used to prevent it from falling over.
● Wear eye protection when using springs
● You will notice that the frequency of the system with the damping card will be less than the
system not using the damping card, even though the mass and spring constant is kept
constant. This is because the system experiences more damping and so will move slightly
slower.
● When comparing your graphs you will see that the maximum amplitude decreases
exponentially in both systems, however the amplitude will decay much faster in the damped
system as the degree of damping is greater.
● A large mass is attached to the spring so that the time period of oscillations is longer,
meaning the maximum amplitude of each oscillation is easier to measure.
● To reduce uncertainty and to more accurately measure the maximum amplitude, you can
record the oscillations of both systems using a position sensor connected to a computer.
equipment Forced oscillations
● Computer
● Position sensor
● Clamp stand
● Spring
● Mass holder
● Signal generator
● Vibration generator
● Metre ruler
methods Forced oscillations
2.Turn on the signal generator and set it to a frequency much lower than the natural
frequency of the spring if it is known - if not set it to 10 Hz. (The natural frequency of the
spring can be calculated by letting the spring oscillate freely and calculating the frequency
of its oscillations.)
3. Wait until the spring stops moving completely, then measure the distance of the bottom of
the mass holder above the sensor using either the position sensor or a metre ruler.
4. Using the position sensor connected to a computer with data-logging software, record the
maximum amplitude of the oscillations above its equilibrium position.
5. Increase the frequency of the signal generator by 10 Hz, and repeat the above step.
6. Repeat the last step until the frequency of the signal generator is far above the natural
frequency of the spring if known, if not, aim for 10 readings.
calculations Forced oscillations
Plot a graph of maximum amplitude against frequency.
As the driving frequency is equal to the natural frequency of the spring when it is
experiencing resonance, you can calculate the natural frequency of the spring using your
graph. You can do this by finding the frequency at which the maximum amplitude of
oscillations reaches its peak value.
safety Forced oscillations
● Be careful when handling the mass holder. If dropped it may cause injury.
● If the clamp stand is unstable, a counterweight placed on the base of the clamp stand can
be used to prevent it from falling over.
● You will be able to see from your graph that the maximum amplitude of oscillations
increases greatly as the frequency of the driving force, which in this case is the vibration
generator, comes closer to the natural frequency. This is because resonance occurs when
the frequency of the driving force is equal to the natural frequency of the spring.
Equipment static methods of deterring spring stiffness
● Clamp stand
● Spring
● 100 g masses with mass holder
● 30 cm ruler
method static methods of deterring spring stiffness
- Measure the original length of the spring using the 30 cm ruler.
- Set up equipment as in the diagram.
- Measure the new length of the spring and record this value.
- Add a 100 g mass to the mass holder and measure the new length of the spring.
- Repeat the above step until the total mass reaches 800 g (including the 100 g mass
holder). - Repeat the entire procedure to get a second value of length for each value of mass and
calculate the mean length.
calculations static methods of deterring spring stiffness
● Calculate the force exerted by each of the recorded masses by calculating their weight:
Weight = m × g
Where m is the mass and g is the gravitational field strength, 9.81 Nkg-1
.
● Draw a table of force exerted against the extension of the spring. You can calculate the
extension by finding the difference between the new length and the original length.
● Use your table to plot a graph of force against extension, and draw a line of best fit.
● Your line of best fit should be a straight line through the origin showing that F and extension
are directly proportional (Hooke’s law).
● Your line of best fit will follow the equation y = mx where y is force (F) and x is the
extension (ΔL), therefore the gradient must be the spring stiffness (k), following the Hooke’s
law equation:
F = k ΔL
y = m x
● Therefore you can calculate spring stiffness by finding the change in force over the change
in extension over a large interval.
methods static methods of deterring spring stiffness
● Be careful when handling the masses. If dropped they may cause injury.
● If the clamp stand is unstable, a counterweight placed on the base of the clamp stand can
be used to prevent it from falling over.
● Wear eye protection when using springs.
● You can reduce uncertainty in measurements of extension by using a spring with a small
spring constant so that the extension is larger.
● Be careful not to exceed the elastic limit of the spring as it will no longer be following
Hooke’s law, and your results will not form a straight line graph.
● As you are measuring static objects you can take your time and so measurement errors are
less likely.
Equipment Techniques and procedures used to investigate
transformers
● 2 C cores (laminated iron cores in a C shape)
● Wire
● Low voltage AC supply
● 2 voltmeters
● 2 ammeters
● Variable resistor
method Techniques and procedures used to investigate
transformers
- Put the 2 C cores together and wrap 5 turns round the primary coil and 10 round the
secondary for a 1:2 ratio. - Connect a voltmeter across both coils and also connect the primary coil to the low
voltage AC supply. - Turn on the AC supply and record the voltage across each coil.
- Keeping the same AC supply repeat the experiment with different turns ratios.
- Now to investigate the relationship between current and voltage for the number of
turns of coil, add a variable resistor to the primary coil circuit and an ammeter to both
circuits. - Keeping the number of turns constant, turn on the power supply and record the
voltages and output current for a range of input currents determined by the variable
resistor.
calculations Techniques and procedures used to investigate
transformers
● For the turn ratios, divide the number of turns on the secondary coil (Ns
) by the
number on the primary (Np
).
● Calculate the ratio in voltage across the secondary coil (Vs
) to voltage across the
primary (Vp
).
● You should find that Ns
/Np= Vs/ Vp.
● For the current investigation you should find that Ns/Np = Vs/ Vp = Ip/Is
.
● The efficiency (e) of the transformer can be found using the circuit with ammeters by
the formula e = IsVs
/ IpVp.
safety Techniques and procedures used to investigate
transformers
● As transformers increase voltage use a low input voltage to keep it at a safe level.
● The formulas won’t quite work as the transformer is not 100% efficient, to increase
the efficiency of the transformer:
○ Use a laminated core to reduce the energy loss by eddy currents.
○ Use low resistance thick copper wire for the coils.
○ Use a magnetically soft material so less energy is needed to magnetise and
demagnetise the core.
○ To increase the amount of magnetic flux generated by the primary coil that
cuts through the secondary, put the coils close together.
Determining the specific heat capacity of a material
Equipment
● Thermometer
● Immersion heater
● Aluminium block with two holes (one for the heater and one for the thermometer)
● Stopwatch
● DC power supply
● Top pan balance
● Insulation for the aluminium block
● Leads
● Ammeter
● Voltmeter
Determining the specific heat capacity of a material
method
- Calibrate the top pan balance and measure the mass of the aluminium block.
Before switching on the power supply, record the temperature of the aluminium block. - Switch on the power supply and simultaneously start the stopwatch.
- Record the voltage on the voltmeter, current on the ammeter and temperature of the
aluminium block every 30 s for 5 minutes. - After 5 minutes, turn off the power supply and measure the highest temperature reached by
the block. This may be a little while after switching off the power supply so keep checking
the temperature every 20 s for the next few minutes until it is clear the temperature is only
decreasing.
Determining the specific heat capacity of a material
calculations
Organise your data in a table with the following columns, calculating power (P) using the
following equation:
= V IP
Where V is the voltage and I is the current.
Using the following equation, calculate the work done (W) by the heater at each 30 second
interval:
= PtW
Where P is the power and t is the time interval (in this case this would be 30 s).
● Find the cumulative value of energy transferred at each 30 second interval by calculating
the sum of the work done up to and including that interval.
● Draw a table of cumulative energy transferred (at each time interval) against the recorded
temperature of the aluminum block at that time interval.
● Use your table to plot a graph of cumulative energy transferred against temperature and
draw a line of best fit.
● Your line of best fit should be a straight line through the origin showing that energy
transferred (Q) and change in temperature (Δθ) are directly proportional.
● Your line of best fit will follow the equation y = mx where y is Q and x is Δθ. You can use
the equation for energy required to change temperature to find what your gradient
represents:
Q = mcΔθ
y = m x
Therefore, the gradient of your graph is equal to mc, where m is the mass of the block and
c is the specific heat capacity of aluminium. This means you can find the specific heat
capacity by dividing your value of gradient by the measured mass of the aluminium block.
Determining the specific heat capacity of a material
safety
● The immersion heater can get extremely hot, therefore it must be fully submerged in the
aluminum block. The aluminum block should also be insulated to prevent any burns.
● The aluminium block can be swapped out for a similar block made of another material to
measure its specific heat capacity.
● The calculated specific heat capacity will be larger than the actual value due to energy
losses to the environment through resistance in the wires in the circuit, and heat being
radiated away from the aluminum block.
● The immersion heater should be touching the aluminum block so that heat can be
transferred easily
Determining the uniform magnetic flux density
between the poles of a magnet using a
current-carrying wire and digital balance Equipment
● Wire
● 2 stands with clamps
● 2 identical magnadur magnets (magnetised along long face)
● Mass balance
● Ammeter
● Power pack
● Ruler
Determining the uniform magnetic flux density
between the poles of a magnet using a
current-carrying wire and digital balance methods
- Set up the wire so it is between the faces of the magnets and both the wire and
magnets are on top of the balance, the ammeter and power pack should be part of
the complete circuit. - With no current flowing, zero the balance.
- Change the supply voltage so that the current, measured on the ammeter, flowing
through the wire is 6.0 A. - Record the reading on the mass balance.
- Repeat the steps and readings for I = 5.0 A, 4.0 A, 3.0 A, 2.0 A and 1.0 .
- Find a second set of results by repeating the experiment.
- Using a ruler measure the length of the magnadur magnets, L, in metres. (This is the
length of wire in the magnetic field).
Determining the uniform magnetic flux density
between the poles of a magnet using a
current-carrying wire and digital balance calculations
● Find the mean reading on the mass balance (m) for each current (I)
● Plot a graph of the mean m against I.
● Draw a line of best fit through the points forming a straight line graph through the
origin and calculate the gradient.
○ The force on the wire is F = BIL (B is the magnetic flux density in Tesla).
○ This is equal to the force found from the balance reading (m) where F =
mg/1000
○ (converting m into kg and with g = 9.81Nkg-1).
○ Hence BIL = mg/1000
○ Make B the subject B =
mg/IL×1000
○ The gradient of the graph is m/I so B = gradient ×
g/L×1000
Determining the uniform magnetic flux density
between the poles of a magnet using a
current-carrying wire and digital balance safety
● When using magnets, students with pacemakers should not be near the magnets as
they can interfere with their pacemaker’s function.
