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4.2 Electrical quantities

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Question 42

A student wants to find the resistance of a constantan wire. They set up a circuit, but make several errors in Western circuit-building conventions:

  1. The battery consists of two cells connected with their positive terminals touching (positive-to-positive).
  2. A voltmeter is connected in series within the main circuit loop.
  3. An ammeter is connected in parallel across the constantan wire.
a.

Explain how each of these three components must be correctly connected to allow the student to safely and accurately find the resistance of the wire.

[3]
b.

After correcting the circuit, the student measures a current of 0.4 A0.4\text{ A}0.4 A through the wire when the potential difference across it is 4.8 V4.8\text{ V}4.8 V. Calculate the resistance of the wire.

[2]
c.

The student then tests two other wires made of the same material. State whether the resistance is higher, lower, or the same compared to the first wire for: (i) a wire that is shorter, but of the same thickness, (ii) a wire that is thinner, but of the same length.

[2]
Markscheme

4.2 Electrical quantities Questions

  1. IGCSE
  2. /Physics
  3. /4.2 Electrical quantities

452 exam-style questions on CIE IGCSE Physics 4.2 Electrical quantities, covering 4.2.1a Positive and negative charge, 4.2.1b Charging by friction and detecting charge, 4.2.1c Electrical conductors and insulators, 4.2.1d Electric fields and electric field patterns, 4.2.2a Electric current, charge and measuring current, 4.2.2b Conduction in metals and the direction of current, 4.2.2c Direct current and alternating current, 4.2.3a Electromotive force, 4.2.3b Potential difference and voltmeters, 4.2.4a Resistance, 4.2.4b Resistance of a metallic wire, 4.2.4c Current–voltage graphs, and 4.2.5 Electrical energy and electrical power. Each one has a worked solution and a mark scheme showing where the marks go.

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