Pracs Flashcards
RP 1 Specific Heat Capacity
- Set up your equipment, ensuring to wrap insulation around of
the base and block. - If the thermometer has an air gap surrounding i when placed in the second hole, drop water into the hole using a pipette to increase thermal contact.
- If the power of the heater is unknown, switch on the power supply and measure the current and potential. Calculate the power using the equation
P = IV
where I is the current (measured in Amps) and V is the potential difference (measured in volts). - Keep the power supply on and start the timer. Measure the temperature of the block every 10 minutes.
- Plot a graph of temperature against work done by the heater. Calculate the gradient of the line.
- Specific heat capacity is the gradient divided by the mass of the block. Since the mass is 1kg, the inverse of the gradient = specific heat capacity of the block.
RP 2 Thermal Insulation
- Set up your equipment, wrapping four of the five beakers with a different insulating material (using the rubber bands to secure the insulation, ensuring as small an air gap between the beaker and insulation as possible).
- The beaker with no insulation wrapped around it is the control beaker.
- Cut circles of cardboard (larger than the mouth of the beaker) to form lids for each beaker.
- Fill each beaker with warm water from the kettle and record the initial temperature of each
- Start the stopwatch and measure the temperature of the beakers every 3 minutes.
- Calculate the change in temperature for each beaker (initial temperature - final temperature).
RP 3 Resistance of a wire
Set up a simple circuit
1. Attach a length of wire along a metre ruler using pieces of tape. Attach a crocodile clip to one end (× = 0cm on the ruler).
2. Attach the second crocodile clip at x = 10cm on the ruler and record both the current and voltage through the wire.
3. Repeat by moving the crocodile clip 10cm along the wire and each time recording the current and voltage measured.
4. Calculate the resistance of the wire at each point using the equation V=IR
5. Plot a graph of the length of the wire (X-axis, units = metres) against the resistance of the wire at that point (y-axis, units 0)
RP 3 Resistance within a circuit
- Construct the circuit
- Switch on the power supply & close the switch. Record the voltage and current
shown. - Construct the circuit shown in diagram 3 (rearrange the resistors from series to parallel).
- Switch on the power supply & close the switch. Record the voltage and ammeter for this circuit arrangement.
The resistors are still the same resistance, so why has the voltage and current changed? - Calculate the total resistance of each circuit, using the equation V=IR.
The total resistances for each circuit should be different. Can you work out how resistance changes depending on how you arrange the resistors (in series or in parallel)?
RP 4 I-V Characteristics
- Construct the circuit shown in the diagram below.
- Set the variable power supply or variable resistor to the lowest setting for potential difference.
- Record the current and voltage over the resistor.
- Increase the current from the power supply by 2V and repeat your readings.
- Change the resistor to a filament lamp and repeat the experiment.
- Change the filament to a diode and protective resistor (to restrict high currents flowing through the diode), ensuring the diode is the correct direction to allow the flow of current through. Change the ammeter to a milliammeter, since the current measured will be smaller than for the other components.
- Plot a graph of current against potential difference for each component.
RP 5 Density of Irregular Shaped Object
1 . Fill the displacement can with room temperature water and align a measuring beaker with the spout. Make sure that the level of water lies below the level of the spout, but that there isn’t too much of a gap between the two levels.
2. Place the irregular shaped object slowly into the can, ensuring not to drop it from a height or cause it to splash.
3. Collect the displaced water and measure the volume of water displaced.
The volume of water displaced will equal the volume of the object that caused the displacement.
4. Measure the mass of the object using a mass-balance.
5. Calculate the density of the irregular object, using the density equation
RP 6 force and extension
1 . Set up your equipment, ensuring the spring will return to its original dimensions if stretched within its elastic limit.
- Attach the pointer to the base of the spring, ensuring that it isn’t angled (parallel to the workbench) and perpendicular to the metre ruler. Align the top of the ruler with the top of the spring.
- Measure the initial length of the spring without any weights attached.
- Add 10g mass to the base of the spring and record the length of the spring.
- Repeat and continue to add masses, ensuring that the spring doesn’t oscillate after each weight has been added.
- Calculate the extension of the spring for each mass by subtracting the initial length of the spring from each different length of the spring.
- Convert all masses to weights using the equation:
Weight (N) = mass (kg) x 9.81 (N/kg) - Plot the graph of force (y-axis) against extension (x-axis). Calculate the gradient. If the spring obeys Hooke’s Law, the graph of force against extension will be linear and pass through the origin. The gradient will equal to 1 / k, where k is the Spring Constant be measured in N/m.
RP 7 Acceleration
- Draw a series of straight lines, each 20 cm apart, perpendicular to the edge of the bench.
- Attach the car to the string at one end, with the other end running across the bench pulley.
- Attach the weight stand to to the loose end of string (you may need to tie a knot at that end, to hook the stand onto). Hold the weight of the pulley, so it doesn’t pull the car but so that the string is fully extended.
- Release the weight stand (allowing it to fall) and begin the timer. Stop timing when the car hits the pulley at the other end of the bench.
To Investigate Changing Force on a Constant Mass:
A. Add 10g mass to the weight stack, holding it so it doesn’t pull the car but the string S fully extended.
B. Release the weights and time the car travelling across the bench.
C. Repeat the experiment by adding 10g weights and recording the time for each.
To Investigate Changing Mass with a Constant Force:
A. Attach a 10g mass on top of the car, using either the Blu-Tac or rubber bands. toy B. Pull the car back to the starting chalk line. C. Release the car and time how long it takes for the car to travel across the bench.
RP 8 Waves in a Ripple Tank
- Fill the ripple tank so the water has a depth of approximately 5mm. Place the ripple tank on top of a piece of white paper or card.
- Place a wooden rod on the surface of the water and attach it to the low-voltage
power supply and motor. Add a lamp to the circuit and hold the lamp above the ripple a tank. - View the wave pattern from the side of the tank. looking through the water.
- To measure the wavelength, place the metre ruler perpendicular to the wavefronts on the page. Measure across as many wavefronts as possible and divide by the number of waves.
- To measure the frequency, count the number of waves passing a particular point In the wave tank over a given time (measure 10 or 20 seconds using a stop clock).
- To calculate the wave speed, multiply the wavelength by the frequency.
RP 8 waves of a vibrating string
- Produce a standing wave on the vibrating string by adjusting the frequency or the generator, the position of the wooden bridge and the tension in the string (by adding or removing masses). A standing wave is created when the wave doesn’t appear to move horizontally, instead the string appears to oscillate only vertically.
- To measure the wavelength, use metre ruler to measure across multiple standing waves and divide by the number of total waves.
The wavelengths of a standing wave is measured across two halves, as shown in the diagram to the left. to
wavelength - To measure the frequency, use a stopwatch to time wave oscillations over ten complete cycles. If the wave S slow enough, time the point at the centre of the half-wavelength, starting at equilibrium and counting every other time the
string passes the equilibrium as a complete cycle. Divide this value by 10 to find the time period. Then use the equation, to find the frequency. - To calculate the wave speed, multiply the wavelength by the frequency.
RP 9 Light
- Slot the collimating slit into the ray box and turn on, producing a narrow ray of light.
- Place the first block of material on top of a piece of paper. Trace around the block using a pencil.
- Draw a normal to the block (a line at 90° to the surface of the block). Align the of at incident ray of light with the meeting point between the normal and the surface of the
block. - Draw the reflected ray and refracted ray, as shown in the diagram below. Remove the block and draw a straight line between the point of reflection and the refracted ray on the other side of the block.
- Using the protractor, measure:
a. The angle of incidence - The angle between the incident ray and the normal.
b. The angle of reflection - The angle between the reflected ray and the normal. C. The angle of refraction - The angle within the material between the normal and the refracted ray. - Repeat the experiment, using a new piece of paper for each different material of block.
RP 10 Radiation and Absorption
1 . Align the infrared detector with one side of the Leslie Cube, 20cm away from the side, and take the initial temperature of the surface.
2. Heat one side of the Leslie Cube by pouring hot water onto the surface.
3. Measure and record the temperature of the surface every 30s for five minutes.
4. Rotate the cube and repeat the experiment for a different surface.
5. Plot temperature (plot on y-axis, measured in °C) against time (plot on x-axis, measured in seconds) for each different surface.
