Year 12 OCR Practicals
These videos are a brief summary of each experiment. They include the theory, equipment, safety considerations and measurements to be taken.
You may find that with the equipment at your school there are some slight variations to the method and how you analyse your data. Please comment on the videos on my YouTube channel if you have any queries or would like to share your experiences with other students.
PAG 1.1 - Calculating 'g' using a Free-Fall Method
Dropping a steel ball bearing through light gates can be used to find the acceleration due to gravity. Recording the time taken for it to fall as you then change the distance between the gates allows a graph to be plotted the the value of 'g' determined.
PAG 1.2 - Investigating Terminal Velocity
There are a lot of ways to investigate the terminal velocity of an object moving through a fluid. You can drop paper cupcake cases, or in this example a ball bearing through bubble bath. The exact set up varies with the equipment at your school, but in this video I explain how you can use video to record the data which is then analysed.
PAG 1.2 [Extension] - Viscosity of a Liquid
This is an extension task that allows you to calculate the viscosity of the liquid that an object is moving through. The equation looks daunting and relies on Stokes' Law, however, once you have measured all the terms you simply input the data to find a value for viscosity.
PAG 1.3 - Velocity and Stopping Distance
A wooden block sliding along a desk can be used to model a vehicle coming to a stop. This investigation is a good introduction to the use of light gates - so lots of information can be recorded quickly as the experiment proceeds.
PAG 2.1 - The Young's Modulus of Copper
This is a straight-forward way to measure the Young's Modulus of a material. Copper wire is often used as it is stretched by weights hung over the edge of the bench, with the small extension carefully measured with a ruler.
Wear eye protection in-case the wire snaps.
PAG 2.2 - Springs in Series and Parallel
This is a straight forward practical where you can investigate how combinations of springs in series or parallel behave when loaded. Be aware that when working with springs you should wear eye protection.
PAG 2.3 - Testing Plastic Bags
In this experiment you can investigate the behaviour of a material other than metal. Plastic bags can be easily tested and due to the manufacturing process may have slightly different characteristics in different directions.
PAG 3.1 - Measuring Resistivity of a Wire
Resistivity is a material property that can be measured by recording the resistance of various lengths of wire of a known cross section. Make sure that you only connect the circuit for a short time to minimise any heating effects of the current.
PAG 3.3 - Internal Resistance of a Cell
You can calculate the internal resistance of a cell by changing the external resistance of the circuit and recording the terminal p.d of the cell. When a graph is plotted the gradient is the negative value of 'r' while the y-intercept should be equal to the e.m.f. of the cell.
PAG 3.3 - Max Power of a Cell
Once you have taken measurements for current and potential difference as a cell is connected to circuits with a changing amount of resistance, you can then work out the power of the cell and plot how this changes as the resistance of the external circuit increases.
PAG 4.1 - Investigating Combinations of Resistors
This practical involves setting up a number of circuits with combinations of resistors in series and parallel. It allows you the opportunity to use a multimeter as an ohmmeter and to see for yourself the relationship between resistance and p.d in a series circuit.
PAG 4.3 - Using Non-Ohmic Devices as Sensors
LDRs and thermistors change their resistance when subject to different light intensities and temperatures. This makes them useful in a potential divider circuits where the potential difference across them also changes which can be used to turn on or off other parts of a circuit.
PAG 5.1 - Measuring the Wavelength of Light
A laser will also diffract and interfere when shone through a diffraction grating. The distance to the first, second and third order maxima can be measured which will then allow the wavelength of the light to be calculated.
Be careful with the laser. Do not look at the beam or any reflected light from a shiny surface.
nustem - Diffraction