required practicals

Question 1

specific heat capacity:

Answer 1

• heater and thermometer in aluminium block (add couple of drops of water, so they don’t get stuck).
• attach the immersion heater to a joulemeter to see how much energy is being passed into the heater.
• read temperature before start, and start stop clock as soon as power supply is switched on.
• turn heater on, leave it for roughly 30 minutes.
• read final temperature of the metal.

Question 2

what are risks and safety precautions for the specific heat capacity experiment?

Answer 2

• the immersion heater/metal can become hot, resulting in burns. allow it time to cool before packing away the equipment, and do not touch it when it’s switched on.

Question 3

thermal insulation:

Answer 3

• 80cm^3 of boiling water into a beaker, cover the top with cardboard, apart from a hole for a thermometer.
• record starting temp. of the water, and start a stopwatch.
• record the temperature of the water every 3 minutes for 15 minutes.
• repeat this process with a range of different insulating materials.

Question 4

what are risks and safety precautions for the thermal insulation experiment?

Answer 4

• keep water away from all electrical equipment.
• do not touch hot water directly, as it can result in burns. instead, place the small beaker (containing hot water) inside a larger beaker to handle it.

Question 5

resistance depending on the length of a wire:

Answer 5

• set up a circuit with a battery, an ammeter in series, a length of wire with a voltmeter in parallel to it, and a closed switch.
• record the length of the wire, turn on the power supply, and record the voltmeter and ammeter readings.
• turn off the power supply, change the length of the wire by a fixed amount, and repeat the process.
• calculate and record the resistance for each length of wire using the equation (r = v/I).

Question 6

what are risks and safety precautions for the length of a wire experiment?

Answer 6

especially with shorter wire lengths, it can heat up enormously, resulting in burns if touched. allow the wire to cool before packing away, only connect the power when taking measurements to avoid overheating.

Question 7

density:

Answer 7

regular object:
- measure the mass using a balance.
- use a ruler to measure the length of each side (length x width x height = volume).
- now multiply this volume by the mass of the object, and that’s the density.

irregular object:
- find the mass of the object using a baance.
- fill a eureka can with water, till it reaches just under the spout.
- place the object in the water. this will displace water, and we can measure how much water is displaced with a measuring cylinder.
- this volume is the same as the volume of the object
- now multiply this volume by the mass of the object, and that’s the density.

Question 8

what are risks and safety precautions for the density experiment?

Answer 8

water spilled from the displacement can can fall on the floor and create a slip hazard. use a measuring cylinder to catch any water and prevent spills.

Question 9

I-V characteristics of circuit elements:

Answer 9

• battery, connected by wires to a resistor. the resistor is in series with an ammeter and a variable resistor. we have a voltmeter in parallel across the resistor.
• use the voltmeter to measure the initial potential difference across the resistor.
• then use the ammeter to measure the current through the resistor.
• record these values in a table.
• adjust the variable resistor, and read the values on the voltmeter and ammeter. do this until you have a range of readings.
• switch the direction of the battery, meaning the direction of the potential difference has reversed. both the voltmeter and ammeter should have negative values.
• continue taking several readings of the potential difference and the current.
• repeat the entire experiment twice more. for the first repeat, replace the resistor with a filament lamp.
• for the second repeat, replace the filament lamp with a diode, and place a resistor in series too, as diodes are easily damaged by high current. this extra resistor will keep the current relatively low and protect the diode.
  > this means the ammeter will have to
  be extra sensitive, so scientists use a
  ‘milliammeter’.

Question 10

what are risks and safety precautions for the I-V characteristics experiment?

Answer 10

• wires and components may become hot after a current has passed through. allow to cool before handling.
• disconnect the power supply when not taking readings to prevent overheating.