Formula & Units

What is the unit of current?

•  $\Omega$  

• C

• A

• W

A battery is connected to a lamp which glows for several minutes.

Which quantity is measured in coulombs?

• the charge passing through the battery

• the current in the lamp

• the electromotive force of the battery

• the energy supplied to the lamp

State the unit of resistance.

• A

• C

• W

• $\Omega$

The volt, V, is the unit of potential difference across a circuit component.

How can the volt also be written?

• JC

• J/C

• ΩC

• Ω/C

A heating element is connected to a power supply of voltage V.The current in the element is I and produces thermal energy E in time t.

What is the correct formula for t in terms of I, V and E ?

• t = EV / I

• t = EI / V

• t = E / VI

• t = VI / E