Basics of electricity Flashcards – AQA A-level Physics (7408)

What is electric current?

The rate of flow of electric charge.

What is the average current when charge $\Delta Q$ passes a point in time $\Delta t$?

$I = \frac{\Delta Q}{\Delta t}$

What unit is electric current measured in, and what is one unit in coulombs per second?

The ampere (A); $1\,\mathrm{A} = 1\,\mathrm{C/s}$.

How is potential difference between two points defined? Give its equation.

It is the work done, or energy transferred, per unit charge moving between the points: $V = \frac{W}{Q}$, where $W$ is work done and $Q$ is charge.

What is the unit of potential difference, and how is it expressed in joules per coulomb?

The volt (V); one volt equals one joule per coulomb.

How is electrical resistance defined in terms of potential difference and current?

It is the ratio of the potential difference across a component to the current through it: $R = \frac{V}{I}$.

What is the unit of electrical resistance, and how is it defined in terms of volts and amperes?

The ohm ($\Omega$); $1\,\Omega = 1\,\mathrm{V}/\mathrm{A}$.