practicalssss :/ Flashcards
Determination of resistivity of a wire
copper wire and crocodile clips
calculate cross sectional area of wire with micrometer
Plot graph of resistance against length
Gradient is equal to resistivity/cross-sectional area
safety – disconnect crocodile clips in between measurements to avoid the wire heating up
investigating the electrical characteristics for a range of ohmic and non-ohmic components
components – copper block, filament lamp and diode
variable resistor
vary the voltage across the component by changing the resistance of the variable resistor
plot graph of mean current against voltage
determining the internal resistance of a cell
circuit of cell with voltmeter in parallel, switch, ammeter and variable resistor
set variable resistor to its maximum value, close the switch and record the voltage and current
Decrease the resistance of the variable resistor and repeat this
plot 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
using non-ohmic devices as sensors
Circuit of cell, LDR and resistor with voltmeter in parallel
alter light intensity
plot graph of voltage across the resistor against light intensity
The line of best fit is a curve
determining the wavelength of light using a diffraction grating
equipment: diffraction grating, laser, screen and ruler
shine a laser through the diffraction grating onto the screen, measure the distance between the central fringe and the one beside it. Measure the distance between the grating in the screen
wavelength = dsin0
determining the speed of sound in air by formation of stationary waves in a resonance tube
equipment: tuning fork, hammer, resonance tube and water reservoir
fill resonance tube halfway with water, hit the tuning fork of a known frequency with hammer and hold it above the tube then lower the water level until the intensity of sound is amplified, when resonance is heard, mark the water level with a rubber band
lower the water further until the next point of resonance is heard and mark it
using the length from the top of the tube to the rubber bands, find the wavelength, repeat the step for each of the Maxima and then calculate the mean wavelength
Multiply the mean wavelength by the known frequency to find the speed of the soundwave
using an oscilloscope to determine the frequency and amplitude of the wave
equipment: oscilloscope, leads, microphone, loudspeaker and musical instrument
Connect the microphone to the oscilloscope input and play one note on the musical instrument into the microphone. Use the oscilloscope to determine the frequency and amplitude of the signal. Compare this frequency and amplitude values to database values to determine the notes played on the instrument and whether it is in tune
Observing the random nature of radioactive decay
equipment: radioactive source, Geiger-Müller tube, clamp stand, tongs, source holder and ruler
1. Set up the clamp stand and attach the GM tube to it
2. calculate the background count by switching on the counter (connected to the GM tube) Record this background count.
3. Remove the radioactive source from its storage box and place it 0.1 m away from the GM tube
4. Switch on the counter and take readings of count for 10 seconds every 30 seconds for 5 minutes.
● Plot a graph of corrected count rate against time
● 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
● Using your curve you can measure the half-life of the radioactive substance
Investigating the absorption of α-particles,
β-particles and γ-rays by appropriate materials
1.calculate the background count by switching on the counter (connected to the GM tube)
2. Using the tongs place the source about 5 cm from the geiger counter, and measure the count rate
3. Place a few sheets of paper in front of the source and repeat the step above.
4. 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.
5. 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.
Investigating the charge of a
capacitor
cell of Capacitor with voltmeter in parallel, Resistor, Cell, Switch, Stopwatch and Ammeter
Close the switch to charge the capacitor, record the voltage and current at time t = 0 and at 5 s intervals as the capacitor charges until about 120s have passed.
Plot a graph of voltage against time, this graph will show an exponential growth curve
Plot a graph of current against time, this graph will show an exponential decrease
The area under the I-t graph gives the charge stored by the capacitor.
Determining the uniform magnetic flux density
between the poles of a magnet using a current-carrying wire and digital balance
- 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 .
- Using a ruler measure the length of the magnets, L, in metres. (This is the length of wire in the magnetic field).
plot graph of mass against current
gradient= BL/g
BIL=mg
