Core Practicals Flashcards
What are the experimental methods in measuring the acceleration of free fall of an object?
- Set up a light gate vertically using a G-Clamp, Clamp Stand and corresponding bosses to secure it in place.
- Determine the distance between the two light gates.
- Record repeat readings of velocity and time for a variety of different heights.
- Plot a graph of Velocity Vs. Time, the gradient of the straight line will give a value for acceleration of free fall.
What are the experimental methods of measuring the resistivity of a wire?
R = PL/A Therefore P = RA/L.
- Set up a wire between two fixed points secured to table using G-Clamps.
- Use an micro meter to measure the diameter of the wire at various points along the wire, taking a mean final value.
- Calculate the cross sectional area of thee wire using the formula A = Pi * r^2.
- Use an ohmmeter to record the resistance of the wire at sensible distance intervals along the wire.
- Plot a graph of the recorded resistances times the constant value for cross sectional area vs. the recorded length intervals.
- The gradient of the straight line graph will give a value for resistivity.
What are the experimental methods of measuring the internal resistance and E.M.F of a circuit?
- Set up a standard test circuit featuring a Cell of known P.D, Variable resistor (In Series), Ammeter (In Series) and a Voltmeter (Parallel to Cell).
- Vary the resistance of the circuit in five or more sensible intervals measuring the corresponding values of V and I.
- y = mx + c and V = E - Ir, therefore a graph of V vs. I will have a y intercept: E and gradient: -r.
What are the experimental methods of measuring the viscosity of a substance?
F = (6) x (Pi) x (n) x (r) x (v) Therefore n = F / ( 6 x Pi x r x v ).
- Measure the mass of the ball using a top pan balance and calculate the weight using the equation W = mg.
- Measure the radius of the sphere using a micrometre/Vernier Caliper.
- Position elastic bands at two positions on the measuring cylinder, measuring the distance between them.
- Using a stopwatch, measure the time taken for the sphere to travel between the two markers through the given substance.
- Using these values, calculate the velocity oft he sphere using the equation S = VT.
- Substitute the recorded values into the formula n = F / (6 x Pi x r x v).
What are the experimental methods of measuring the Young’s Modulus of a wire?
- secure one end of a wire between two blocks of wood secured to the table using a g-clamp
- place the other end of the wire on a pulley on the end of the table and hang a mass to the end. this will be our force.
- affix two pieces of masking tape to the wire and record the initial distance between them
- hang another mass on the end and record the distance between the two pieces of tape and the diameter of the wire with micrometre
- use equation pi r squared to calculate area
- repeat this for around 5 masses ( a preliminary experiment may need to be done to determine the approximate order of magnitude for the force required to stretch the material to its yield point)
-Plot a graph of mass added against extension.
-Measure the gradient of the straight portion of the graph and use this to calculate the Young
modulus for the copper.
What are the experimental methods of Determining the speed of sound in air using a 2-
beam oscilloscope, signal generator, speaker and microphone
The oscilloscope will display on two traces the signal fed to the loudspeaker and the signal
received by the microphone. As the distance between the microphone and the speaker is
increased, the phase of the signals varies and the traces on the screen move past each other.
2. Place the microphone next to the oscilloscope and place the speaker about 50 cm away, facing
the microphone. Turn on the signal generator and set it to about 4 kHz. Adjust the oscilloscope
to show the microphone signal with about three cycles on the screen.
3. Connect the signal generator output to the second oscilloscope input (as well as the speaker)
and adjust the controls to display three cycles of this signal.
4. Adjust the spacing on the screen and the distance between the speaker and microphone so
that the bottom of one trace is just level with the top of the other.
5. Adjust the separation so that a trough on the top trace exactly coincides with a peak on the
lower trace. Place the metre ruler alongside the microphone and speaker and record the
distance between the microphone and speaker.
6. Move the speaker away from the microphone and observe one trace sliding over the other.
Move the speaker so that the trace has moved exactly one cycle. The troughs and peaks
should just touch again. Record the new distance between the microphone and speaker. The
difference between the two distances is one wavelength.
7. Continue to move the speaker away from the microphone and record each successive distance
where the peaks of one trace coincide with the troughs of the other.
8. Calculate a mean value for the wavelength of the sound and estimate the uncertainty in this
measurement.
9. Use one of the traces to determine the freque
