2. SI Units Flashcards

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1
Q

Intro spiel

who / why invented them

whats the benefit

A

The creation of the decimal metric system began during the eighteenth-century French revolution when two platinum standards, representing the metre and kilogram, were placed in the Archives de la République in Paris.

Eminent scientists like Gauss and Weber then went on to promote the universal application of a standard system of measurement in the early nineteenth century.

By the 1960s, the International System of Units (abbreviated to SI units from the French Le Système International d’Unités) was developed which incorporated six base units (the mole was added later) along with rules for the use of derived units and prefixes. The advantage of this unified system is that equations and calculations will produce answers in the appropriate SI unit. Unfortunately, they are not used universally.

A question concerning the SI units is a popular opening to the physics SOE and candidates should understand the relationship between derived and base units and be comfortable in manipulating them from one to the other.

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2
Q

SI Units

A
Base unit Name Symbol
Length              metre m
Mass                 kilogram kg
Time                  second s
Current              ampere A
Temperature     kelvin K
Am of sub         mole mol
Lums intens     candela cd
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3
Q

What are the two

supplementary units?

A

The plane angle (radian) and solid angle (steradian) were supplementary units
but this category was abolished in 1995. These units are considered named
derived units.

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4
Q

List some of the derived units

A

Derived units are formed by combination of
various base units according to
mathematical relationships
which link these quantities.

Derived units Name Symbol
Area square metre m2
Volume cubic metre m3
Density kilogram per cubic metre kg/m3
Velocity metre per second m/s
Acceleratrion metre per second squared m/s2

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5
Q

Derived Named SI UNITs

A

Force

Pressure

Energy

Power

Electric charge

Electric potential difference

Capacitance

Electrical resistance

Magnetic flux

Magnetic flux density

Inductance

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6
Q

Pressure

A

Pressure pascal (Pa) N/m2 kg·m–1·s–2

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7
Q

Energy

A

Energy joule (K) N·m kg·m2·s–2

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8
Q

Power

A

Power watt (W) J/s kg·m2·s–3

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9
Q

Electric charge

A

Electric charge coulomb (C) – A·s

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10
Q

Electric potential

difference

A

Electric potential difference

volt (V) W/A kg·m2·s–3·A–1

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11
Q

Capacitance

A

Capacitance farad (F) C/V kg–1·m–2·s4·A2

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12
Q

Electrical

resistance

A

Electrical resistance

ohm (Ω) V/A kg·m2·s–3·A–2

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13
Q

Magnetic flux

A

Magnetic flux

weber (Wb) V·s kg·m2·s–2·A–1

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14
Q

Magnetic flux

density

A

Magnetic flux density

tesla (T) Wb/m2 kg·s–2·A–1

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15
Q

Magnetic flux density

A

Magnetic flux density

tesla (T) Wb/m2 kg·s–2·A–1

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16
Q

Inductance

A

Inductance henry (H) Wb/A kg·m2·s–2·A–2

17
Q

Temperature

A

Temperature degree celsius (°C) – K

18
Q

Bigger SI Unit prefix

A
Factor	Name 	Symbol
1024	yotta	Y
1021   	zetta	Z
1018 	exa	         E
1015 	peta	P
1012 	tera	          T
109  	giga	        G
106  	mega	M
103  	kilo	        k
102	       hecto	h
101    	deka	da
19
Q

Smaller SI Unit prefix

A
Factor	Name 	Symbol
10-1	        deci	           d
10-2	        centi	    c
10-3	        milli	          m
10-6         micro	    µ
10-9  	nano	   n
10-12	pico	            p
10-15	femto	    f
10-18	atto	            a
10-21	zepto           z
10-24	yocto           y