Quantities
Before calculating anything you have to know what is being measured. A force goes in newtons and an energy in joules, and mixing them up is not a slip of vocabulary: they are different things. The clue is nearly always in the unit itself, because almost all of them are built from others — a watt is a joule per second, so it is a rate of spending and not an amount; a newton is kilogram-metre per second squared, so it is a pull and not a reading on a scale. This rung practises the question that comes before all the others: what is this measured in?
Where this sits
Exercises from this rung
Generated by the app, from easiest to hardest
What is an electric charge measured in?
- coulomb (C)
- ampere (A)
- joule (J)
- pascal (Pa)
Why The coulomb (C) is one ampere for one second. The unit nearly always tells you what the quantity is: reading it slowly saves memorising it.
easierWhat is a resistance measured in?
- ohm (Ω)
- newton (N)
- volt (V)
- ampere (A)
Why The ohm (Ω) is one volt for each ampere it lets through. The unit nearly always tells you what the quantity is: reading it slowly saves memorising it.
in betweenWhat is an energy measured in?
- pascal (Pa)
- watt (W)
- volt (V)
- joule (J)
Why The joule (J) is one newton applied along one metre. The unit nearly always tells you what the quantity is: reading it slowly saves memorising it.
harder