Practical skills Flashcards
(RP1) Describe how you would investigate the variation of the frequency of stationary waves on a string with length, tension and mass per unit length of a string.
Equipment: signal generator, vibration generator, clamp stand, pulley, wooden bridge, 100g masses with holder, metre ruler, 1.5m string, balance
Method:
- Attach string through vibration generator to stand with a counterweight at one end, and a bridge and on a pulley behind with a loop for weights to be hooked, with the distance between the vibration generator and bridge being 1m using metre ruler
- Increase frequency using signal generator until string oscillates at first harmonic, measure frequency and repeat this reducing l by 0.1m each time down to 0.5m
- Repeat experiment 2 more times to find and record the mean f for each l
- Measure mass of string on balance and record it
Graphs/calculations:
- Plot graph of mean f against 1/l and draw line of best fit (wave speed = 2m)
- T = weight of hanging mass
Safety:
- Use counterweight on stand to avoid it toppling over and causing injury
- Place sand tray to reduce risk of injury if weights fall off end of string
(RP2) Describe of you would investigate interference effects using Young’s double slit experiment.
Equipment: laser, double slit, white screen, metre ruler
Method:
- With lab being darkened, place laser behind a single slit behind a double slit pointing at the screen
- Ensure distance between screen and double slit is 0.5m using metre ruler
- Measure across a large number of fringes using ruler and divide the number of fringe widths to find w
- Increase D by 0.1m and repeat each time up to 1.5m
- Repeat the experiment 2 more times and find and record mean w for each D
Graphs/calculations:
- Plot graph of w against D and draw line of best fit
- Wavelength of laser light = m x slit separation
Safety:
- Ensure lasers are pointed away from people’s eyes as it could be dangerous to shine in someone’s eyes
(RP2) Describe of you would investigate interference effects using a diffraction grating.
Equipment: laser, diffraction grating, white screen, metre ruler
Method:
- Ensuring lab is darkened, place laser behind diffraction grating pointing at screen
- Measure D to be 1m
- Measure distances between order 2 and 0, and order 1 and 1 either side of central maximum using ruler and find mean of each
Graphs/calculations:
- Slit separation + reciprocal of number of slits per metre
- Find wavelengths using formula and angles and find mean
Safety:
- Ensure lasers are pointed away from people’s eyes as it could be dangerous to shine in someone’s eyes
(RP4) Describe how you would determine the Young Modulus of a steel wire.
Equipment: 2 1.5m steel wires, main scale and vernier scale, 1kg masses and 2 1kg holders, micrometer, metre ruler
Method:
- Set up comparison wire with a main scale next to a test wire with a lined up vernier scale with both wires attached to a beam on ceiling
- Measure the initial length (l) of the test wire with a metre ruler
- Add 1kg mass holders to both wires so they are taut and record initial scale reading
- Add an additional 1kg mass to test wire and record new scale reading, find extension (new reading - initial reading) and record it
- Repeat this adding 1kg each time up to 8kg
- Repeat experiment 2 more times and find mean e for each m
- Measure diameter of test wire at various points along it using micrometer to find and record mean diameter
Graphs/calculations:
- Find cross-sectional area of wire
- Find force on test wire for each m by calculating mg
- Plot a graph of F against e and draw line of best fit
- Young Modulus is l x gradient divided by area
Safety:
- Wire could break and injure eyes when stretched tightly, so wear safety goggles
- If wire breaks masses could fall and cause injury, so sand tray should be placed under them to catch them
(RP5) Describe how you would determine the resistivity of a wire.
Equipment: 1m long constantan wire, voltmeter, ammeter, low voltage power supply, micrometer, metre ruler
Method:
- Measure diameter of wire at various points along it using micrometer and find/record mean
- Set up voltmeter in parallel to wire attached to series circuit with crocodile clips and an ammeter
- Adjust length of wire to 0.1m using clips and metre ruler
- Read/record current on ammeter and pd on voltmeter, find resistance and record this
- Increase length by 0.1m and repeat this, increasing it by 0.1m each time up to 0.8m
- Repeat experiment 2 more times, find/record mean R for each l
Graphs/calculations:
- Calculate cross-sectional area
- Plot graph of mean R against l and draw line for best fit
- Resistivity is m x A
Safety:
- Disconnect clips between measurements to avoid wire heating up and causing burns if touched, if current rises too high reduce pd using variable power supply
- If wire is tight, wear safety goggles in case it snaps and injures eyes
(RP6) Describe how you would investigate the EMF and internal resistance of electric cells and batteries.
Equipment: battery/cell, voltmeter, ammeter, variable resistor, switch
Method:
- Set up voltmeter in parallel with battery, in series with switch, ammeter and variable resistor
- With switch open record reading V on voltmeter
- Set variable resistor to its max value, close switch and record V and reading on ammeter, opening the switch between readings
- Decrease resistance of variable resistor and repeat this, obtaining pairs of readings of V and I over the widest possible range
Graphs/calculations:
- Plot graph of V against I and draw line of best fit
- y-intercept is emf and m is negative internal resistance
Safety:
- Another resistor could be included in series with the other to avoid high currents which could be dangerous and make wires get hot and cause a burn
