Electric current Flashcards – Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028)

What is electric current?

The rate of flow of electric charge.

What does a current of one ampere mean?

One coulomb of charge passes a point each second.

What equation relates constant current $I$ to charge transferred $Q$ and time taken $t$?

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

In which direction is conventional current defined to flow?

From positive to negative, the direction in which positive charge would flow.

What does an ammeter measure, and in what unit?

Electric current, in amperes.

How is an ammeter connected to measure current in a circuit?

In series, so the current being measured passes through it.

How do analogue and digital ammeters display their readings?

An analogue ammeter uses a pointer and scale; a digital ammeter displays a number.

What must the selected ammeter range accommodate?

The expected current.

Which ammeter range should you start with if the current is unknown, and why?

Start with a higher range to help avoid exceeding the meter’s range.

What is the advantage of using a lower suitable ammeter range?

It can give a more precise reading.

Which scale should you read on an analogue ammeter?

The scale corresponding to the selected range.

How do free electrons and positive metal ions differ in their ability to move through a metal?

Free electrons can move through the metal; positive metal ions remain in fixed positions.

What happens to free electrons in a metal when a potential difference is applied?

They have a net movement through the metal, transferring charge.

How does the direction of electron movement in a metal compare with conventional current?

Electrons move in the opposite direction to conventional current.

How do direct current (d.c.) and alternating current (a.c.) differ in their direction of flow?

D.c. flows in one direction; a.c. repeatedly reverses direction.

Must the magnitude of a direct current be constant?

No. Its magnitude can vary as long as its direction does not reverse.