# Measuring Variables(Edexcel International A Level Physics)

Author

Katie M

Expertise

Physics

## Measuring Variables

• When measuring a variable in an experiment, it is important to use the most appropriate instrument and measuring technique to achieve the most accurate value for that measurement
• A list of the common apparatus and their purpose is shown in the table below:

Apparatus and Their Purpose Table

 Experimental Instrument Purpose Example Metre ruler To measure the length of an object of a length between 1 cm - 1 m Length of a wire Vernier Calipers To measure short lengths between 0.1 mm - 1 cm Extension of a wire Micrometer Screw Gauge To measure very short lengths between 0.01 mm – 0.1 mm Diameter of a wire Top-pan Balance To measure the mass of an object Weight of a block Protractor To measure angles Measuring angle of refraction of a beam of light Stopwatch To measure time Time taken for an oscillation Thermometer To measure temperature Temperature increase for specific heat capacity of a material Voltmeter To measure potential difference Potential difference across a bulb Ammeter To measure current Current through a bulb Oscilloscope To display waves and measure their frequencies Frequency of a signal Laser To provide a monochromatic, coherent source of light Investing the interference of light

• The key factor associated with choosing the appropriate instrument is its resolution
• If the resolution of an instrument is too big, then it won't be able to measure small measurements

#### Exam Tip

When planning experiments, make sure to really think about which instrument you need to measure the length of something. A rough rule could be:

• Length will be between a few cm – 1 cm, use a ruler
• Length will be between 0.1 mm – few cm, use a vernier caliper
• Length will be between 0.01 mm – 0.1 mm, use a micrometer

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