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CAIE IGCSE Physics 4.2.2.2 Use of ammeters (analogue & digital)

Practise placing ammeters correctly in circuits, reading how current changes, and judging when a laboratory meter is unsuitable.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • draw an ammeter symbol in series with the lamp, LED or resistor measured
  • choose the circuit position that measures total current or current in one component
  • state why very large or brief currents can exceed an ammeter range

4.2.2.2—Use of ammeters (analogue and digital) question 1

[Maximum number: 1]

A lightning conductor protects a tall building and the people in it against damage and injury caused by lightning strikes.

The lightning conductor is a very long strip of copper that is attached to the side of the building. At the top of the building, the strip of copper is connected to a vertical metal pole and at the bottom of the building, it is buried in the ground.

Fig. 7.1

Fig. 7.1

The bottom of the thundercloud is negatively charged.
As the cloud moves closer to the building, the top of the metal pole becomes charged.

As the cloud passes over the building, a lightning strike occurs and a charge of 0.84 C flows through the lightning conductor. The charge flows for 3.5×10−5 s3.5 \times 10^{-5} \mathrm{~s}.

It is suggested that the current in the lightning conductor could be measured by connecting a laboratory ammeter between the pole and the copper strip.

State one reason why this cannot be successful.

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