Physical Quantities and Units

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Physical Quantities and Units by Mind Map: Physical Quantities and Units

1. Electric Current (SI Unit: Ampere or A)

2. Mass (SI Unit: Kilogram or kg)

2.1. Standard Mass

2.1.1. The standard kilogram is the mass of a certain cylindrical piece of platinum-iridium alloy kept at the International Bureau of Weights and Measures at Sevres, France.

2.2. Instruments of measurement

2.2.1. The electronic beam balance is a very common instrument. Accuracy: +/- 0.1g

2.3. Note: Mass and Weight are different. Do not confuse the two.

3. Time (SI Unit: Second or s)

3.1. Definition

3.1.1. 9 192 631 700 times the period of oscillation of radiation from the cesium atom.

3.2. Instruments of measurement

3.2.1. The analogue stopwatch is an common instrument. Accuracy: +/-0.1s

3.2.2. The digital stopwatch is an extremely common instrument. Accuracy: +/-0.01s

3.2.2.1. Note: Human reaction error = 0.3s

3.2.3. Other uncommon instruments: pendulum, watches and ticker-tape timers.

4. Thermodynamic Temperature (SI Unit: Kelvin or K)

5. Luminous Intensity (SI Unit: Candela or Cd)

6. Amount of substance (SI Unit: Mole or mol)

7. Length (SI Unit: Metre or m)

7.1. Definition

7.1.1. Length of the path travelled by light in a vacuum during a time of 1/299792458 0f a second.

7.2. Instruments of measurement

7.2.1. Metre rule is a common instrument to measure metres. Accuracy: +/-0.01m

7.2.2. Vernier Calipers are less common but are still used. Accuracy: +/- 0.01cm

7.2.3. The Micrometer Screw Gauge is rarer but still often used. Accuracy: +/-0.01mm

7.3. Official Length

7.3.1. The official length of the metre was the distance between two lines on a specific bar of platinum-iridium alloy stored under controlled conditions.