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Physics Paper 1 Practicals (I-V characteristics (Ohmic conductor eg. fixed…
Physics Paper 1 Practicals
Specific heat capacity
Measure the mass of the block, then insulate it to reduce the energy transferred from the block to the surroundings eg. with newspaper
Insert the thermometer and heater into the two holes in the block
Measure the initial temp of the block and set the pd of the power supply to 10V, then turn on the power supply and start a stopwatch
When the power is turned on, the current in the circuit does work on the heater, transferring energy electrically from the power supply to the heaters thermal energy store
This energy is transferred to the materials thermal energy store via heating, causing the materials temp to increase
As the block heats up, take readings of the temp and current, or of the joulemeter every minute for 10 mins - the current shouldn't change
After 10 readings, turn off the power and calculate the specific heat capacity using the reading from the joulemeter, or by finding the power using P = VI, then finding the energy transferred using E = Pt
Factors affecting resistance
Resistance depends on factors such as whether it's parallel or series or the length of wire
Length of wire
Attach a crocodile clip to the wire level with 0 on the ruler
Attach a second crocodile clip to the wire and write down the length of wire between the 2 clips
Close the switch and then record the current in the wire and the pd across it
Open the switch, and move the second clip further back, then record the new length, pd or current
Repeat this with a number of different lengths
Calculate the resistance using V = IR, then plot a graph of length against resistance
Graph should be a straight line through the origin,a s resistance is directly proportional to to length
I-V characteristics
Graphs which show how current flowing through a component changes as the pd is increased
By varying the variable resistor this alters the current flowing through the circuit and the pd across the component
Linear components have a straight line on their graph eg. ohmic conductor
Non-linear components have a curve on their graph eg. filament lamp or a diode
Take several pairs of readings from the ammeter and voltmeter to see how the pd varies as the current changes
Repeat each reading twice to get an average pd
Swap the wires connected to the cell so they become reversed so the direction of current is reversed
Plot a graph of current against voltage for the component
Ohmic conductor eg. fixed resistor
Current through an ohmic conductor, at constant temperature, is directly proportional to the potential difference
Graph is a straight line
Filament lamp
As the current increases, the temp of the filament increases, so the resistance increases, so then the current decreases
The graph is a curve steep at first but becoming more shallow
Diode
Current will only flow through a diode in one direction, so the diode has a very high resistance in one direction
Graph is a steep line on one side of the graph
Resistance
Adding resistors in series
Need at least four identical resistors
Build a circuit with the resistor, a battery and an ammeter - make sure the pd of the battery is recorded
Measure the current through the ammeter, then calculate the resistance of the circuit using V = IR
Add another resistor in series, and then calculate the resistance again
Do this until all of the resistors have been added, then plot a graph of number of resistors against total resistance - should be a straight line
Adding resistors in parallel
Using the same equipment, build the initial same circuit
Measure the total current of the circuit and calculate the resistance of the circuit using V = IR
Add another resistor, but in parallel
Measure the total current through the circuit and again calculate the overall resistance of the circuit
Repeat until all resistors are added, then plot a graph of number of resistors against total resistance - should be asymptotic, starts high then decreases at a decreasing speed, tending towards 0 but never reaching it
Density of materials
Find the density of a solid object
Use a balance to measure its mass
If it's regular, measure its length, width and height then calculate density using p = m/v
For an irregular solid, submerge it in a eureka can filled with water, then see how much water is displaced, as this is equivalent to vol of the object
Then place the vol and mass into the formula p = m/v
Density of a liquid
Place a measuring cylinder on a balance and set it to 0
Pour 10ml of liquid into the measuring cylinder and record the liquids mass
Pour another 10ml, and repeat the process until the cylinder is full while recording the total vol and mass each time
For each measurement, find the density of the liquid
Finally, take an average if the calculated densities
Thermal insulators
Boil water in a kettle, then pour some into a sealable container, and measure mass of water in the container
Use a thermometer to measure the initial temperature of the water
Seal the container and leave it for 5 mins - use a stopwatch
Measure the temp after 5 mins, then pour away the water and allow the container to cool to room temperature
Repeat the experiment, but wrap the container in an insulator like foil or newspaper once sealed
Make sure the starting mass and temperature of the water are constant
The lower the temp difference after 5 mins, the better an insulator it is
You can also investigate the effectiveness of the thickness of a material
