Edexcel International A Level Physics

Revision Notes

3.1 Identifying Apparatus

Identifying Apparatus

  • When planning an experiment, the first step is to identify the apparatus required
    • Each experiment will have its own unique set of apparatus
  • The apparatus is the equipment needed to carry out the experiment
    • This includes both what you are measuring and how you are measuring it
  • Common apparatus include:
    • Metre rulers - to measure distance and length
    • Balances - to measure mass
    • Protractors - to measure angles
    • Stopwatches - to measure time
    • Ammeters - to measure current
    • Voltmeters - to measure potential difference
  • More complicated instruments such as the micrometer screw gauge and Vernier calipers can be used to more accurately measure length

3-1-measuring-instruments

Examples of apparatus used in scientific experiments

  • The apparatus required depends on what you are trying to measure
  • A few examples are shown in the table below

Apparatus Table

Quantity Apparatus
Length Metre ruler, Micrometer, Vernier caliper
Mass Top–pan balance
Angle Protractor
Time Stopwatch
Temperature Thermometer
Potential difference Voltmeter
Current Ammeter
Frequency Oscilloscope

  • An example of apparatus for measuring the specific heat capacity of an aluminium block is shown below:

Specific Heat Capacity Apparatus

Apparatus needed to measure specific heat capacity

  • This includes:
    • A block of the substance (preferably 1kg in mass) or in the case of a fluid, a beaker containing a known mass of the fluid
    • A thermometer
    • An appropriate heater (e.g. an immersion heater)
    • A power source
    • A joule meter or a voltmeter, ammeter and stop-clock (I will assume we have the latter)
    • Wires and connectors

Worked example

The diagram below shows one possible method for determining the Young modulus of a metal in the form of a wire.Practical Apparatus Worked Example, downloadable AS & A Level Physics revision notesDescribe how you can use this apparatus to determine the Young modulus of the metal. The sections below should be helpful when writing your answers.

  • The measurements to be taken.
  • The equipment used to take the measurements.
  • How you would determine Young modulus from your measurements.

Step 1: State the necessary measurements to be taken

    • The diameter of the wire
    • The initial length of the wire
    • The extension of the wire (final length – initial length)
    • The mass of the hanging masses or the weight applied to the wire

Step 2: State and explain which equipment would be the most suitable

For measuring the diameter of the wire:

    • A micrometer screw gauge or vernier callipers
    • Micrometer would be best as this has the highest resolution when measuring small areas

For measuring the original length / extension of the wire:

    • A metre ruler or a tape measure
    • The wire has a moderate length which cannot be measured using a vernier scale

For measuring extension:

    • Travelling microscope
    • These are designed for measuring small changes in length

For measuring the mass:

    • Scales or a top-pan balance
    • A top-pan balance would be best as this has the higher resolution
    • W = mg equation can be used to calculate weight

For measuring the weight directly:

    • A newton-meter
    • This is useful if ‘known’ weights are used and to check if the quoted masses are accurate

Step 3: Explain how Young's modulus can be determined from these measurements

    • Young modulus is equal to the gradient of a stress-strain graph (in the linear region)
    • Stress is equal to:

Tensile Stress Equation

    • Strain is equal to:

Tensile Strain Equation

Where:

    • F = weight (N)
    • A = cross-sectional area of wire (m2)
    • ΔL = extension (m)
    • L = original length (m)

  • Young's modulus for this metal is then calculated using the following equation:

Young's modulus using graph, downloadable AS & A Level Physics revision notes

Exam Tip

When listing the apparatus for an experiment, make sure you've referred to every last piece of equipment, even the small parts such as wires and power supplies 

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