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Physical Quantities and Their Units

Falling force (weight) acts on a mass
Level 2 (without higher mathematics)
Level 2 requires school mathematics. Suitable for pupils.
Updated by Alexander Fufaev on
Table of contents
  1. Force
  2. Angular momentum
  3. Torque
  4. Energy
  5. Power
  6. Pressure
  7. Charge
  8. Voltage
  9. Resistance
  10. Electric field
  11. Magnetic field
  12. Capacitance
  13. Inductance
  14. Thermal capacity (heat capacity)

Energy

Symbol: \(W\)
Unit of energy: \(\mathrm{J}\) (Joule)
Example: \( W ~=~ 30 \, 000 \, 000 \, \mathrm{J} \) is the energy released when one kilogram of coal is burned.

Derived units of energy
Formula anchor

Power

Symbol: \(P\)
Unit of power: \(\mathrm{W}\) (Watt)
Example: \( P ~=~ 2000 \, \mathrm{W} \) is the power of a kettle.

Derived units of power
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Pressure

Symbol: \(\mathit{\Pi}\)
Unit of pressure: \(\mathrm{Pa}\) (Pascal)
Example: \( \mathit{\Pi} ~=~ 100 \, 000 \, \mathrm{Pa} \) is the air pressure of the earth's atmosphere.

Derived units of pressure
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Mechanical Pressure (Force per Area) on a Plate
Pressure is force per area.

Charge

Symbol: \(Q\)
Unit of charge: \(\mathrm{C}\) (Coulomb)
Example: \(Q ~=~ 1.6 \cdot 10^{-19} \, \mathrm{C} \) is the charge of an electron.

Derived units of charge
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Electric positive / negative charge - attraction and repulsion
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Positive and negative charges.

Voltage

Symbol: \(U\)
Unit of voltage: \(\mathrm{V}\) (Volt)
Example: \(U ~=~ 100 \, 000 \, 000 \, \mathrm{V} \) is the voltage between a thundercloud and the earth.

Derived units of voltage
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Relationship between voltage and kinetic energy
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Voltage is energy per charge.

Resistance

Symbol: \(R\)
Unit of resistance: \(\mathrm{\Omega}\) (Ohm)
Example: \(R ~=~ 100 \, \mathrm{\Omega} \) is the resistance of an ohmic conductor to which 200 volts are applied and through which 2 amps flow.

Derived units of resistance
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Simple circuit with one resistor
Electrical resistance in a simple circuit.

Electric field

Symbol: \(E\)
Unit of electric field: \( \frac{ \mathrm{V} }{ \mathrm{m} } \) (Volt per meter)
Example: \(E ~=~ 1000 \, 000 \, \frac{ \mathrm{V} }{ \mathrm{m} } \) is the electric field between the bottom and top of a thundercloud.

Derived units of the electric field
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Two positive charges - electric field lines
Electric field of two positive charges.

Magnetic field

Symbol: \(\class{violet}{B}\)
Unit of magnetic field: \( \mathrm{T} \) (Tesla)
Example: \(\class{violet}{B} ~=~ 20 \, \mathrm{T} \) creates a superconducting coil in a nuclear fusion reactor.

Derived units of magnetic field
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Magnetic Field Lines of a Current-Carrying Coil
Magnetic field of a current-carrying coil.

Capacitance

Symbol: \(C\)
Unit of capacitance: \( \mathrm{F} \) (Farad)
Example: \(C ~=~ 100 \, \mathrm{\mu}\mathrm{F} \) is the capacitance of a given capacitor.

Derived units of capacitance
Formula anchor
AC voltage applied to a capacitor
A capacitor with a certain capacitance in an alternating current circuit.

Inductance

Symbol: \(L\)
Unit of inductance: \( \mathrm{H} \) (Henry)
Example: \(L ~=~ 500 \, \mathrm{mH} \) is the inductance of a given coil with current flowing through it.

Derived units of inductance
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Inductive reactance of the coil in AC circuit
Coil with a certain inductance in an AC circuit.

Thermal capacity (heat capacity)

Symbol: \(C\)
Unit of thermal capacity: \( \frac{\mathrm{J}}{\mathrm{K}} \) (Joule per Kelvin)
Example: \(C ~=~ 4190 \, \frac{\mathrm{J}}{\mathrm{K}} \) is the heat capacity of one liter of water.

Derived units of heat capacity
Formula anchor
Temperature change of water by supply of thermal energy
Water has a certain heat capacity