Core Practicals Flashcards
1
Q
Determine the acceleration of a freely falling object
A
- Open switch to break connection between battery and electromagnet and turn on timer
- Electromagnet demagnetises causing steel ball to fall a distance, h, from bottom of ball to trap door (h measured with ruler)
- When ball falls through trap door, connection of timer to battery is broken, so timer stops
- Record time taken for ball to fall h metres, repeat 3 times and find average
- Vary h and record t for each
- Use t^2 = 2/g * h, as s = ut + 1/2 at^2
- Plot graph of t^2 against h, draw line of best fit, m will be 2/g, so g = 2/m
2
Q
Determine the Electrical Resistivity of a Material
A
- At various points along the wire measure diameter, d using a micrometer and find average
- Find Area using A = πr^2
- Measure length of wire using a ruler
- Attach crocodile clip to wire and measure V and I from voltmeter and ammeter
- Find R using R = V/I
- Repeat every 10cm and record R for each length
- Plot graph of R against L and draw line of best fist
- Resistivity is gradient * A
3
Q
Determine the EMF and Internal Resistance of an Electrical Cell
A
- Vary I in the circuit by changing R using the variable resistor. Measure V for different values of I
- Record data for V and I in a table and plot results on a graph of V against I
- Start with E = V + Ir, rearrange to get V = -rI + E, which is the equation of the straight line
- Y intercept is E. Gradient is -r
4
Q
Determine the Viscosity of a Liquid
A
- Fill a wide, clear tube with liquid you want to measure, make sure you know density of the liquid
- Put one rubber band around halfway down the tube at a position such that the ball bearings will have reached terminal velocity when they reach it
- Place two more rubber bands, below the first at equal distances apart, these will be where your record t1 and t2
- Measure diameter of ball and halve to find radius
- Drop ball bearing into tube, start stopwatch when it reaches first band and record time it takes to reach other bands
- Repeat at least 3 times
- Calculate average time taken for ball to fall between bands to calculate terminal velocity of the ball
- Calculate viscosity using viscosity equation
5
Q
Determine the Young’s Modulus of a Material
A
- Use a long, thin wire, to increase extension and therefore reduce uncertainty
- Use a micrometer to measure the diameter of the wire, then halve to get radius, then use πr^2 to find area
- Clamp wire to bench so you can hang weights off it, add a marker on the wire which you will measure from
- Add smallest weight needed to straighten wire and record this length as the unstretched length
- Increase the weight in equal steps e.g. 100g, and record length for each weight, using the marker, find extension for each weight by taking away unstretched length from measured length
- Use measurements to find stress and strain and use young modulus equation (E = σ/ε)
6
Q
Determine the Speed of Sound in Air
A
- Set frequency of signal generator to around 2-6kHz. A 2-beam oscilloscope must be used as it can display 2 waves, 1 for the signal generator generating a sound wave and 1 for the same sound wave being received by the microphone
- The oscilloscope has 3 dials, 2 are gain dials an other is the timebase dial, adjust dials so you can see at least one complete cycle of each wave
- Change distance between microphone and loudspeaker so that peaks of 1 wave line up with troughs of another and then measure this distance
- Calculate frequency by measuring period and using f = 1/T. This will give lower uncertainty than just reading from signal generator
- Move the microphone away from the loudspeaker so that the microphone’s corresponding wave on the oscilloscope moves 1 full wavelength along the signal generator’s wave, measure this new distance
- The difference in the two recorded distances is the wavelength of the sound wave
- Repeat multiple times and find an average wavelength and use v = fλ to find the speed of sound
7
Q
Factors affecting the Frequency of a Vibrating String
A
- Measure mass and length of strings using a balance and a ruler, then find mass per unit length (μ = M/L)
- Set up apparatus with 1 string. Record μ, measure and record L and work out tension using T = mg
- Turn on signal generator and vary frequency until you find a stationary wave with a node at each end and 1 antinode. This is the frequency of the 1st harmonic
- λ = 2L, f = 1/2L * √T/μ, v = √T/μ
- Measure how L affects f, keep μ and T constant, move the vibration transducer towards and away from the pulley, find 1st harmonic, record f against L
- Measure how T affects f, keep μ and L constant, add and remove masses to change T, find 1st harmonic, record f against T
- Measure how μ affects f, keep L and T constant, but use different string sample to change μ, find 1st harmonic, record f against μ
8
Q
Determine the Wavelength of Light
A
- Position a laser in front of a diffraction grating so that the light travels through the grating and creates an interference pattern on a flat wall or screen a few metres away
- Measure distance, D, between the diffraction grating and the wall
- Measure distance, x, between zero order maximum and 1st order maximum for both sides and take an average of the 2 readings
- Using x and D, the angle between 1st order and zero order can be calculated using small angle approximations, θ = x/D
- Use d sinθ = nλ to calculate wavelength
- Repeat for more orders and find an average for the wavelength
- Repeat experiment with diffraction grating with different distance between slits
9
Q
Investigating Change in Momentum
A
- Set up apparatus, connect light gates to a data logger and computer
- Hold trolley at one end of the air track and then release it. The hanging mass will fall, pulling the trolley along the track
- Total mass of system is equal to the sum of the mass on the trolley and the hanging mass
- Use data logger and computer to find velocity of trolley at each gate. Use this to calculate momentum, p=mΔv
- You can also use data logger to find time taken to travel between the 2 gates, which can be used to work out rate of change of momentum, Δp/Δt
- Repeat 3 time to find an average
- Force acting on the system equals weight of hanging mass, F = mg
- Repeat experiment for varying masses, each time you remove a mass place it on the trolley, so total mass is constant
- Plot a graph of F against Δp, graph will be straight, showing F = Δp / Δt
10
Q
Use ICT to analyse Collisions between Small Spheres
A
- Record the masses of the 2 ball bearings using a balance
- Position two metre rulers at right angles to each other, place 1 ball bearing on the table and position a camera above the table so it has a birds eye view
- Start the camera recording, then roll the 2nd ball towards the stationary ball so they collide
- When both balls have come to rest stop the recording and use video analysis software to study the collision
- If you know the time between each frame, you can work out how many frames in each 0.1 seconds
- Go through frame by frame and use rulers to find the distance travelled by each ball, in horizontal and vertical directions every 0.1 seconds. The use Pythagoras to find the magnitude of each ball’s velocity before and after the collision, use trigonometry to find the direction
- To show momentum is conserved, calculate momentum before and momentum after
11
Q
Analyse the PD across a charging and discharging Capacitor
A
- Set up a circuit with a DC power supply, high resistance resistor, switch, capacitor, ammeter and a voltmeter around the (originally discharged) capacitor
- Close switch to charging position and start the timer
- Record V and I every 10 seconds
- Repeat 3 times and calculate averages
- Plot graph of I against t, and of V against t
12
Q
Calibrate a Thermistor in a Potential Divider circuit as a Thermostat
A
- Set up a circuit with a power source, a fixed resistor, a thermistor and an ohmmeter
- Set up a Bunsen burner, tripod, gauze, beaker with ice, stirring rod, mercury thermometer to 0.5 C and a waterproof thermistor
- The temperature of the water changes in 2-5°C increments from 0 to 100°C (using crushed melted ice to get to 0°C and putting the thermistor in the boiling water to reach 100°C)
- Allow time for the temperature to reach equilibrium, stir the water and ensure the thermistor is completely submerged in the water
- Measure the resistance using the ohmmeter
- Vary temperature and record resistance
- Plot a graph of R against T
- Use the graph to find the resistance at a given temperature, and use to set up a potential divider circuit using: Vout = Vin × R1 / (R1 + R2)
13
Q
Determine the Specific Latent Heat of a Phase Change
A
- Set up apparatus
- Weigh each of the beakers and record their initial mas
- Crush the ice an put it in the funnel
- Fully submerge the immersion heater into the funnels of ice, one heater switched on and another not, as a control. Start the timer
- Record V and I across the heater
- After 5 minutes, switch off the heater and record the final mass of water in each beaker
- Calculate the total mass of water melted in the 5 minutes, by finding difference between initial and final
- Mass of ice melted by heater = Total mass melted - Mass melted due to heat from surroundings
- L = VIt / Δm
14
Q
Investigate the relationship between Pressure and Volume of a Gas
A
- A fixed mass of gas is trapped by oil in a sealed tube with fixed dimensions
- Increase the pressure of gas slowly by using the tyre pump to increase the pressure on the oil (so that the level of oil rises and the air will compress)
- Measure pressure on the gauge and the volume of the gas from the column
- Wait 30 seconds for the temperature of the liquid to return to room temperature
- Find at least 7 data values for pressure and corresponding volume
- Repeat 3 times and find the average volume for each pressure
- Plot pressure against 1/volume to find the relationship, gradient is nRT
15
Q
Investigate the Absorption of Gamma Radiation by Lead
A
- Set up a Geiger counter and radioactive source, with a clamp and sheet of lead between them
- Before the radioactive source is removed, record the background radiation count on the GM tube over a period of time (5-10 minutes)
- Plant the source in the source holder and point at the GM Tube
- Measure the thickness of each lead sheet at various points using a micrometer and find an average
- Add each sheet 1 by 1, recording the count after each 1
- Repeat 3 times and find the average for each sheet
- Count Rate = Number of Counts / Time Elapsed
- Calculate the corrected count by subtracting background radiation count for each reading
- Plot corrected count rate against thickness
