All Experiments

Question 1

1) Investigate the motion and collisions of objects. Apparatus may include trolleys, air-track gliders, ticker timer, light gates, data-loggers and video techniques

Answer 1

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Question 2

Determine the acceleration of free fall using only a ruler, an object and a timer

Answer 2

Acceleration of freefall:

1) Take the object, and measure the height from which it will be dropped using a metre ruler.
2) Using a timer measure the time taken for the object to fall and land at the bottom of the measured distance (e.g. from 1m to the ground).
3) Repeat this several times to get a more accurate measure as there is a large uncertainty due to human reaction time.
4) Use the time and distance to calculate an AVERAGE value of g:

s = ut + 1/2(at^2)

Initial velocity is 0 therefore this becomes:
s = 1/2(at^2)

Rearrange for a:
2s/t^2 = a

To improve accuracy, ou could use lightgates which will provide very accurate readings for time, thus eliminating the largest cause of error – human reaction time.

Also, this is an average value as there is air resistance, however we are ignoring it so this value deviates from the actual value of 9.81.

Question 3

2) Determine the acceleration of free fall in the laboratory using trapdoor and electromagnet arrangement or light gates and timers

Answer 3

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Question 4

3) Determine terminal velocity in fluids, e.g. ball-bearing in a viscous liquid it comes in air

Answer 4

1) Get a vertical tube, and fill it with a viscious liquid. (e.g. wallpaper paste).
2) Using a metre ruler, mark regular. consecutive intervals using tape or a rubber band. For example, mark every 10cm on the tube.
3) Drop a ball bearing into the tube, and using a timer, record the time taken for the ball bearing to reach each individual interval.
4) Repeat this several times (at least 3) and use these to calculate an average value for the time taken.

Using these average values, you can calculate the velocity (distance of each interval/time taken).

5) Plot this on a velocity x time graph and draw a line of best fit (which is representative of the acceleration).

You should observe a linear section, and then it eases off into a straight line. Where the linear section ends and flattens out, is the terminal velocity.

Question 5

4) Investigate force-extension characteristics for arrangements which may include springs, rubber bands, polythene strips

Answer 5

Hooke’s Law:

1) Hang the test wire vertically on a clamp, against a ruler so you can measure it with ease.
2) Measure the origin vertical length when there is no mass attacked to it.
3) Add a mass of known weight, regularly, measuring the new length of the test wire.
4) Record this data and use it to plot a graph of force (weight of mass) and the corresponding extension.

If the line of best fit is linear, then the material is said to obey Hooke’s Law.

Question 6

5) Investigate the electrical characteristics for a range of ohmic and non-ohmic conductors

Answer 6

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Question 7

6) Determine the resistivity of a metal

Answer 7

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Question 8

7) Determine the internal resistance of a chemical cell or other source of e.m.f.

Answer 8

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Question 9

8) investigate potential divider circuits which may include a sensor such as a thermistor or an LDR

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Question 10

9) Use an oscilloscope to determine frequency

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Question 11

10) Demonstrate wave effects using a ripple tank

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Question 12

11) observe polarising effects using microwaves and light

Answer 12

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Question 13

12) investigate refraction and total internal refraction of light using ray boxes, including transparent rectangular and semi-circular blocks

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Question 14

13) Superposition of experiments using sound, light and microwaves

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Question 15

14) Determine the wavelength of light using a double-slit and a diffraction grating

Answer 15

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Question 15

Describe an experiment using Polaroid’s

Answer 15

Polaroids:

This is a method to check if a wave is plane polarised:

1) Set up the source around 1 meter from a detector. In this example we’ll use microwaves so set up the microwave transmitter opposite the detector which will be connected to a meter which will show the intensity of microwaves deteccted.
2) Hold a diffraction grating between the the detector and emitter. The reading on the detector should be at a maximum, showing that the wave is travelling through the diffraction grating.
3) Slowly rotate the diffraction grating through 90 degrees. You should observe that the intensity decreases as it is rotated, as the wave can no longer travel through the diffractoin grating. This shows the the wave is polarised perpendicular to the direction of the grating slits.
4) As you rotate it again through every 90 degrees, you should see the intensity increase and decrease. At 360 degrees, you will observe the original reading.
5) This shows that the wave is plane polarised, and the vibrations are in 90 degrees to the direction of energy transfer – confined to the plane of the diffraction grating when the detector reading is at a maximum.

Same idea applied to polaroids, where the polaroid absorbs the light if the slit is perpendicular to plane polarised wave.

Question 16

15) Determine the speed speed of sound in air by formation of stationary waves in a resonance tube

Answer 16

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Question 17

16) Techniques and procedures used to determine the Young’s modulus for a metal.

Answer 17

Young Modulus:

1) Using a micrometer, measure the diameter of the wire in several places and find an average (this is done to find the cross sectional area)
2) Clamp the wire down horizontally, with it hanging over a pulley on one side, with a ruler reading 0cm at the clamp.
3) Using the ruler (metre ruler), mark the wire at a specific place and read the initial length.
3) Add a mass of known weight (1N or 2N), and then measure the length again from the clamp to where the marker on the wire has now moved. You can find the extension by doing new length - original.
4) Repeat this, with increasing the weight hanging over the end of the wire.
5) You can use this data to find the stress and strain using the formulas, and then plot a graph of stress against strain. The gradient of this line is equal to the Young Modulus – but only the LINEAR section of the line of best fit.

Question 18

Determine the Planck constant experimentally

Answer 18

Planck Constant:

This experiment will require a cell, ammeter, voltmeter, resistor and LED lights of varying colours/wavelengths.

1) Attach an LED to the circuit using a flying lead to complete the circuit, and start with the resistor on maximum resistance.
2) Using some sort of tube, look at the light on the LED to see when the LED first starts to emit light. Simultaneously, turn the resistor down very slowly.
3) When the light first begins to be emitted, record the corresponding voltage and current for that wavelength. This is the “threshold frequency”.
4) Repeat this fro LEDs with varying wavelengths.
5) Use the data recorded to plot a graph of Voltage (threshold) no the y-axis and 1/wavelength on the x axis.

The gradient of the graph is equal to V/Wavlength, since V = eV, we can rearrange this:

eV = hc/wavlength 
V = hc/ wavelength*e

Now rearrange into the form y = mx + c:

V = hc/e * 1/wavelength

So using the graph we can calculate the planck constant (estimate):

Planck constant = gradient * 1/wavelength

Question 19

Techniques and procedures used for an electrical method to determine the specific heat capacity of a metal block and a liquid

Answer 19

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Question 21

Techniques and procedures used for an electrical method to determine the specific latent heat of a solid and a liquid.

Answer 21

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Question 22

Techniques and procedures used to investigate PV = constant (Boyle’s law) and P / T = constant.

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Question 23

Techniques and procedures used to investigate circular motion using a whirling bung.

Answer 23

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Question 24

Techniques and procedures used to determine the period/frequency of simple harmonic oscillations

Answer 24

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Question 25

Techniques and procedures used to investigate capacitors in both series and parallel combinations using ammeters and voltmeters.

Answer 25

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Question 26

Techniques and procedures to investigate the charge and the discharge of a capacitor using both meters and data-loggers.

Answer 26

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Question 27

Techniques and procedures used to determine the uniform magnetic flux density between the poles of a magnet using a current-carrying wire and digital balance.

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Question 28

Techniques and procedures used to investigate magnetic flux using search coils.

Answer 28

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Question 29

Techniques and procedures used to investigate transformers.

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Question 30

Techniques and procedures used to investigate the absorption of α- particles, β-particles and γ-rays by appropriate materials.

Answer 30

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Question 31

Techniques and procedures used to determine the half-life of an isotope such as protactinium.

Answer 31

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