Identifying Apparatus (Edexcel International A Level Physics)

• 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

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:

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

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:

• • Strain is equal to:

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: