Paper 3

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Diya

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  • Analogue meters

    • continuous data, allowing for precise readings
    • information signal that has the same variations with time as the information itself
  • Digital meters

    • discrete data
    • can display measurements with greater resolution
    • reduces reading errors due to parallax
  • Standing wave method- fundamental frequency
    1. Record the mass used and mass of the string using a balance
    2. By moving adjustable bridge and using a ruler, ensure length of string is 1m
    3. Using signal generator increase the frequency until the string oscillates at it's first harmonic
    4. Record this value, by reading off signal generator
    5. Move the adjustable bridge by 0.1m to decrease the length of the string
    6. Adjust the frequency using the signal generator until the string is at it's first harmonic and record this value
    7. Continue adjusting the bridge to further decrease the length of the string by 0.1, adjusting the signal generator and taking readings until the length of the string is 0.5m
    8. Repeat this process twice and calculate a mean value for the frequency at every distance of L
  • Graph and calculations for standing wave
    Plot results, 1/f against length, where gradient will be 2/c
  • How to investigate tension for standing waves?
    different masses to change the tension
  • Double slit method
    1. Ensure room is darkened
    2. Using a ruler, adjust distance between paper and laser to 0.5m
    3. Measure across as many fringes possible, counting number of fringes used and divide the measurement with this number to find fringe width
    4. Adjusting the paper and using a ruler increase the distance by 0.1m and recalculate fringe width
    5. Repeat this until the distance reaches 1.5m
    6. Repeat experiment for mean width
  • Double slit, what if slit separation is unknown?
    use vernier callipers
  • Graph and calculation for double slit
    plot w against D where gradient can be multiplied by slit separation for wavelength
  • Safety aspects for double slit experiment
    Shining a laser into someone’s eyes can be dangerous, so ensure that the lasers are pointed away from them
    Ensure no way the laser can reflect
  • Diffraction Grating method
    1. Ensuring room is partially darkened, set up the apparatus
    2. By using a ruler and adjusting the screen, ensure distance is 1m
    3. Measure the distances and on either side of the central maximum using a ruler
  • Calculation for diffraction grating
    using the distance between central maxima and first order calculate angle using arctan(h/d) and use this to find wavelength
  • Finding value for g method
    1. Set up the apparatus
    2. Using a metre rule ensure the distance between the gates is 0.5m
    3. Turn on the electromagnet and attach the ball bearing.
    4. Reset the stopwatch to zero and switch off the electromagnet.
    5. Read and record the time t on the stopwatch
    6. Reduce height, h, by 0.05m by moving the lower light gate upwards and repeat this, reducing h by 0.05m each time down to 0.25m
    7. Repeat the experiment twice more and find and record the mean t for each h
  • Calculation for finding g
    plot graph of 2h/t against t
    2ht=\frac {2h}{t} =gt+ gt +2u 2u
    will be a form of y = mx + c
  • Young's Modulus
    1. Measure the diameter of the test wire at various points along it using the micrometer, taking a minimum of 3 readings and find the mean diameter
    2. Set up apparatus including test and comparison wire
    3. Add a 1kg mass holder to both wires so they are taut and record the initial scale reading
    4. Add an additional 1kg mass to the test wire and record the new scale reading
    5. Find its extension by subtracting the initial scale reading from this and record it
    6. By adding another 1kg mass, repeat this adding 1kg each time up to around 8kg
  • Calculation and graph for Young's modulus
    • Calculate the cross-sectional area A of the wire
    • Find the force F on the test wire for each m by calculating mg
    • Plot a graph of F against e and draw a line of best fit where gradient only gives F/e so need to multiply gradient with L/A
  • Safety risk in young modulus
    The wire will be stretched very tightly and could break and injure eyes, so safety goggles must be worn
  • Why used an additional comparison wire in youngs modulus?
    compensates for sagging of the beam and thermal expansion effects and provides a reference point against which to measure the extension
  • How to reduce uncertainty in Young's Modulus?
    The original length of the test wire should be as long as possible
  • How to reduce parallax error in determining value of g?
    in measuring the height, the ruler can be clamped directly next to the light gates
  • How to reduce effect of air resistance when determining g?
    ball use should be dense
  • Resistivity Method
    1. Measure the diameter of the constantan wire at various points along it using the micrometer and find and record the mean diameter
    2. Set up apparatus
    3. Adjust the length of wire to 0.1m using the crocodile clips, measured using the metre ruler
    4. Read and record the current on the ammeter and the voltage on the voltmeter
    5. Calculate the resistance by using R=V/I and record this
    6. Increase length by 0.1m and repeat this, increasing it by 0.1m each time up to 0.8m
  • Calculations and Graph for resistivity

    Plot a graph of the mean value of R against l and draw a line of best fit
    where resistivity is given by gradient x cross-sectional area
  • Safety for resistivity?

    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
  • Reducing uncertainty in resistivity?
    The wire should be free from kinks and held straight so the measurement of the length is as accurate as possible
  • EMF method
    1. With the switch open, record the reading on the voltmeter
    2. Set the variable resistor to its maximum value, close the switch and record the voltage and the reading on the ammeter
    3. Open the switch between readings and decrease the resistance of the variable resistor
    4. Repeat this, obtaining pairs of readings of voltage and current over the widest possible range
  • Calculation and graph for EMF and Internal resistant
    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
    V=V =ϵ−Ir \epsilon -Ir
    is y = mx + c
  • What should the batteries be in emf method?
    fairly new
  • Mass-spring method

    1. Set up the apparatus with no masses slotted on the 50g holder
    2. Pull the mass hanger vertically downwards a few centimetres and release it
    3. Start the stopwatch when it passes the fiducial marker
    4. Stop the stopwatch after 10 complete oscillations and record this time
    5. Divide time T by 10 to find the time period of the mass-spring system and record this
    6. Add a 50g mass to the 50g holder and repeat this, adding 50g each time up to 500g, recording the total hanging mass m and corresponding time period T for each
    7. Repeat the experiment twice more and find and record the mean time period for each mass
  • Mass-spring calculations and graph
    Plot a graph of T^2 against m and draw a line of best fit
  • What do you in mass spring if it moves horizontally?
    stop the oscillation and start it again making sure it is pulled vertically downwards
  • Improvements for mass spring?
    A motion tracker and data logger
    eliminates random error in starting and stopping the stopwatch
  • Simple Pendulum method
    1. Set up the apparatus
    2. Adjust the point of suspension so that the distance from that point to the centre of mass of the pendulum bob is 1.5m
    3. Pull the pendulum to the side and release it so that it has a small amplitude and travels in a straight line
    4. Start the stopwatch when it passes the fiducial marker
    5. Stop the stopwatch after 10 complete oscillations and record this time
    6. Divide time by 10 to find the time period of the pendulum and record this
    7. Decrease the length by 0.1m and repeat this, reducing length by 0.1m each time down to 0.5m
    8. Repeat the experiment twice more and find and record the mean time period for each distance
  • What type of pendulum should be used and why?
    small pendulum bob so that it is easier to measure the length to its centre of mass
  • For simple pendulum what must angle displaced be?
    should be no more than about 15 degrees
  • Boyle's Law method

    1. Measure the inside diameter d of the syringe using a vernier caliper
    2. Replace the plunger and draw in about 4.0ml of air and record this
    3. Fit the rubber tubing over the nozzle and clamp it with the pinch clip as close to the nozzle as possible
    4. Set up the apparatus as shown in the diagram, with only the 100g holder and one 100g mass suspended
    5. Gently move the plunger up and down to ensure it is not sticking and release it
    6. Record the new volume on the syringe scale and add two 100g masses to the holder
    7. Repeat this, adding two 100g masses each time until the total mass is 1000g
    8. Repeat the experiment twice more and find and record the mean volume for each mass
  • Graph for Boyle's law
    Plot a graph of 1/V against P and draw a line of best fit. A straight line through the origin should be obtained, showing that the pressure is inversely proportional to the volume
  • Charles Law method
    1. Set up the apparatus with the open end of the capillary tube at the top and add hot water from the kettle
    2. The hot water should cover the air sample
    3. Stir the water well using the thermometer and read and record the value of its temperature and the length of the air sample on the 30cm ruler
    4. Allow the water to cool by 5°C and repeat this, taking measurements every 5°C down to room temperature
  • Calculation and graph for Charles Law method
    Plot a graph of length against temperature, draw a line of best fit, and find the gradient m
    l1=l_1 =mθ1+ m{\theta}_1 +c c
    where absolute zero can be calculated by
    θ0=\theta_0 =θ1−l1m \theta_1 -\frac{l_1}{m}
  • Discharging Capacitor
    1. Set up the apparatus
    2. Set the switch to be connected with battery to allow the capacitor to fully charge
    3. Move the switch to be connected with resistor and start the stopwatch
    4. Observe and record the voltage reading at time t=0 and at 5s intervals as the capacitor discharges until about 120s have passed.
    5. Repeat the experiment twice more and obtain the average voltage at each time interval
  • Graph and Calculation for discharging resistor
    • Calculate the natural logarithm of voltage at each time interval.
    • Plot a graph of ln(V) against t and draw a line of best fit.
    • This should give a straight line graph with negative gradient, showing that the decay of voltage across the capacitor is exponential