Physics Practicals P1 n P2

Specific Heat Capacity

Improvements:

• Add more insulation.

• Use a lid to reduce heat loss.

• Repeat and remove anomalies.

• Measure the mass of the metal block using a balance.

• Record the initial temperature of the block using a thermometer.

• Place an immersion heater and thermometer into the holes in the block.

• Wrap the block in insulation to reduce energy transfer to the surroundings.

• Connect the heater to a power supply, ammeter and voltmeter.

• Record the potential difference and current.

• Turn on the heater and start a stopwatch.

• Heat the block for a fixed amount of time.

• Record the final temperature of the block.

• Calculate the temperature change.

• Calculate the energy supplied using:

E=IVt

• Calculate the specific heat capacity using:

c=E/mΔT

• Repeat and calculate a mean.

Resistance of a Wire

Control variables:

• Material of wire.

• Thickness of wire.

• Temperature of wire.

Improvements:

• Switch off between readings to stop heating.

• Use thinner wire for clearer results.

• Set up a circuit with a power supply, ammeter and test wire in series.

• Connect a voltmeter across the test wire.

• Use a metre ruler to measure the length of the wire being tested.

• Change the length of the wire using a crocodile clip.

• Record the current and potential difference for each length.

• Calculate the resistance using: R = V / I

• Repeat for several different lengths.

• Repeat readings and calculate a mean.

• Plot a graph of resistance against length.

I–V Characteristics

• Set up a circuit containing the component, ammeter and variable resistor in series.

• Connect a voltmeter across the component.

• Change the resistance using the variable resistor to vary the potential difference.

• Record the current and potential difference for each reading.

• Reverse the power supply to obtain negative values.

• Repeat for a range of voltages.

• Plot a graph of current against potential difference.

For a filament lamp:

• Resistance increases as temperature increases.

For a diode:

• Current only flows in one direction.

For a resistor at constant temperature:

• Current is directly proportional to potential difference.

Density

Improvements:

• Ensure object is fully submerged.

• Read measuring cylinder at eye level.

Irregular

• measure mass

• use a top pan balance or scales

• part fill a measuring cylinder with water

• measure initial volume

• place object in water

• measure final volume

• volume of object = final volume − initial volume

• fill a displacement / eureka can with water

• water level with spout

• place object in water

• collect displaced water

• measuring cylinder used to determine volume of displaced water

• use of: density = mass volume

Regular

• Measure the mass using a balance.

• Measure dimensions using a ruler or calipers.

• Calculate the volume using the correct equation.

• Calculate density using: density = mass ÷ volume.

• Repeat measurements and calculate a mean.

• Measure carefully to reduce uncertainty.

Force and Extension

Improvements:

• Use a pointer to reduce parallax error.

• Repeat readings and calculate a mean.

• Clamp a spring vertically next to a ruler.

• Measure the original length of the spring.

• Add a known mass and allow the spring to stop moving.

• Measure the new length of the spring.

• Calculate the extension.

• Repeat with increasing masses.

• Convert mass to force using:

W=mg

• Plot a graph of force against extension.

Conclusion:

• Extension is directly proportional to force until the limit of proportionality.

Acceleration

mprovements:

• Use a longer time interval.

• Measure several wavelengths and divide by the number counted

• Place a ripple tank on a flat surface.

• Turn on the light source and wave generator.

• Use a ruler to measure the wavelength.

• Count the number of waves passing a point in a set time.

• Calculate frequency using:

​ f = number of waves/ time

• Calculate wave speed using:

• v = fλ

• Repeat and calculate a mean.

Radiation and Absorption

Improvements:

• Use lids to reduce heat loss by evaporation.

• Repeat and calculate a mean

Control variables:

• Volume of water.

• Starting temperature.

• Time interval.

• Fill metal cans with equal volumes of hot water.

• Use cans with different surface finishes (matt black and shiny).

• Place a thermometer in each can.

• Record the starting temperature.

• Leave for a fixed amount of time.

• Record the temperature at regular intervals.

• Compare the temperature changes.

Conclusion:

• Matt black surfaces are the best absorbers and emitters of infrared radiation.

• Shiny surfaces are poor absorbers and emitters.