Recall that an ammeter is connected in series with a component to measure…

The idea

An ammeter measures the current through a component, so it must sit in the same path as that component: the circuit is broken and the ammeter inserted so that the current passes through it in series. If the ammeter were connected in parallel across a component, it would offer a second route and would not measure the current in that component. Current is measured in amperes, symbol A; the unit 'amp' is the everyday name for the ampere. To measure the current in a lamp, place the ammeter between the cell and the lamp on the same loop, note the reading in A, then reverse the connections if a negative reading appears. Choose the series position, not a parallel one, and read the value in amp.

What earns the marks

• States that the ammeter is connected in series with the component whose current is being measured.
• Identifies the ampere (amp, symbol A) as the unit of current.
• Rejects a parallel connection because it would divert current rather than measure the current through the component.
• Recognises that the circuit must be broken to insert the ammeter into the same path as the component.

Common mistakes and how to put them right

• Places the ammeter in parallel with the component.

  Put it right: Connect it in series instead.

• Gives the volt as the unit of current.

  Put it right: Use the ampere (amp) instead.

• Connects the ammeter across the cell only.

  Put it right: Insert it in the same loop as the component being measured.

Exam tips

• Read the question for the word 'series' and check the option places the ammeter in the same path as the component.
• Eliminate any option that puts the ammeter in parallel, since that changes the circuit rather than measuring its current.
• Confirm the unit offered is the ampere or amp, not the volt or the ohm.