REQUIRED PRACTICALS Flashcards
(30 cards)
how to find the resonance frequency RP1
start by measuring the mass and lengths of string of different types using a mass balance and ruler.
then find the mass per unit length for each string
set up by having a signal generator and vibration transducer on a bench, attached to one side of the string. the string then goes along over a pulley off the bench with mass attached to the other end.
turn on the signal generator and vary the frequency of the vibration transducer.
find the first harmonic
can change length, tension and mass per unit length to see how frequency changes
how to set up the young’s modulus double slit experiment RP2
either use two coherent light sources or shine a laser through two slits.
the slits have to be around the same size as the wavelength of the laser light so that its diffracted
what will you see on the screen from the double slit experiment
A pattern of light and dark fringes, depending on whether destructive or constructive interference is taking place
what would happen if you use white light in the double slit experiment?
the diffraction pattern would be less intense, with a wider maxima. the pattern would also contain different colours with a central wide fringe due to a mixture of frequencies in white light.
laser safety precautions
lasers can be very dangerous as laser light is very direct, powerful beam of monochromatic light
to avoid damage:
never shine laser towards a person
wear laser safety goggles
avoid shining laser beam on a reflective surface
turn off laser when not needed
what did Youngs double slit experiment show?
that light can have the nature of a wave as it can diffract through two narrow gaps to form an interference pattern.
what should you find the relationship between landa and distance to be when investigating diffraction grating interference? RP2
as landa increases so should distance
how can you work out the fringe spacing of a certain order maximum? (diffraction grating) RP2
measure using a ruler
by using different laser sources or coloured filters to select certain wavelengths of white light
to you could change the diffraction grating to vary d
or change D by moving observation screen
how can you demonstrate a two-source interference pattern? RP2
for water, use one vibrator which drives two dippers
for sound, connect one oscillator to two loudspeakers
for microwaves, attach two microwave transmitter cones to a signal generator.
how can you determine g using freefall? RP3
-drop a ball bearing onto a trap door using an electromagnet
-measure the height from the bottom of the ball bearing to the trapdoor
-flick the switch to simultaneously start the timer and disconnect the electromagnetic, releasing the ball bearing
-the ball bearing falls, knocking the trap door down and breaking the circuit which stops the timer
-repeat 3 times and find an average time then repeat but dropping the ball from different heights
-plot a graph h-t^2 to find g
what’s the most significant source of error when determining g using freefall?
random error for the value taken for height. uncertainty of the ruler 1mm
and there’s a small systematic error if there’s a delay in the switch or timing mechanism
how can you measure internal resistance and emf of a cell or battery? RP6
set up circuit- battery in series with ammeter and voltmeter. variable resistor in parallel with switch.
1.set the variable resistor to the highest resistance
2.close the switch and record the current and pd
3.open the switch and close it again 2 more times to calculate mean current and pd
4.decrease the resistance of the variable resistor and then repeat previous steps with this resistance
5.keep decreasing the resistance till you have 10 readings
6.plot a V-I graph for mean data and draw line of best fit
finding the resistivity of a material experiment RP5
1.set up a circuit, power supply connected to an ammeter, the test wire is clamped to a ruler, the other side of the power supply is attached to a switch and a flying lead. voltmeter in parallel
2.calculate the cross sectional area of the test wire using a micrometer
attach the flying lead to the end of the test wire and measure the length of the test wire
3.close the switch and measure current and pd
4.open the switch again and calculate resistance for current and pd
5.repeat this and take a mean
then repeat this at different lengths of wire
6.plot a graph resistance-length and draw line of best fit
7.find resistivity by multiplying gradient by cross-section area of wire
investigating the mass-spring system RP7- process
attach a trolley to a spring, pull it to one side by a certain amount then let it go
the trolley will oscillate back and forth as the spring pulls and pushes it in each direction
you can measure the time period by getting a computer to plot a displacement-time graph from a data logger connected to a position sensor
what are the three variables you can investigate by using a mass-spring system?
mass, spring content, amplitude
mass-spring system with variable as mass experiment RP7
change the mass by loading the trolley with masses
T^2 against mass graph as they should be directly proportional
mass-spring system with variable as spring content experiment RP7
change the spring constant by using different combinations of springs
plot a graph T^2 against 1/k as they should be directly proportional
mass-spring system with variable as amplitude experiment RP7
change the amplitude by pulling the trolley across by different amounts
plot T against A, T should remain constant as A increases
simple pendulum experiment RP7
attach a simple pendulum to an angle sensor and computer
use to computer to plot a displacement time graph and read off time period from this
you can change one variable at a time and see what happens
should show T^2 directly proportional to length
OR
hang the pendulum from a clamp and timing the oscillations using a stopwatch, use a fiducial marker
the Youngs modulus experiment RP4
-set up a bench and clamp a wire fixed at one end with a pulley at the other which you will hang weights off
-test wire should be thin and as long as possible
-first find cross sectional area of the wire using a micrometer for the diameter in several places and take an average x pi r^2
-start with the smallest weight necessary to straighten the wire
-measure the distance between the marker and fixed end of wire- this is the un stretched distance
-then increase weight in 100g intervals recording the marker each time to get extension
-then use results to calculate stress and strain and plot a stress-strain graph
how to investigate capacitors discharging RP9
-open the switch and remove the power source and add a voltmeter and ammeter and data logger connected to computer
1. close the switch and allow the capacitor to discharge through the resistor
2. when the reading through the ammeter reaches 0, use the computer to calculate the charge on the capacitor over time
3. the computer can then plot a variety of graphs showing how the current, pd and charge vary over time
what do the current-time, pd-time and charge-time graphs look like for a capacitor discharging through a fixed resistor?
all decreasing exponentially
investigating the inverse square law RP12
-taking measurements of intensity at different distances from a gamma source using a Geiger counter
-set up a Geiger counter connected to a geiger-muller tube with one end at the end of a ruler
-turn on the Geiger counter and take 3 readings then an average for the background radiation
-carefully place the radioactive source at a distance d from the tube
-record the count rate at that distance, take three readings
-move the source so the distance is doubled between it and the tube again take 3 readings
-repeat step 5 for 3d, 4d, 5d …
-once finished, put away radioactive source immediately
-average the count rate for each distance and eliminate background radiation
-plot a graph of corrected count rate- distance of the tube from the source, you should see that as the distance doubles, the corrected count rate will drop to a quarter of its value
how to have safe handling of radioactive sources RP12
-always hold a source away from your body when transporting it through the lab
-long handled tongs should be used to minimise the radiation absorbed by the body
-sources of gamma radiation should always be stored in a lead box
-only keep gamma radiation out of the box for the shortest time possible
