A student carries out an experiment to determine the resistance per unit length of a wire YYY. They measure the potential difference VVV across wire YYY for several different currents III. The results are shown in the table below:
| I/AI / \text{A}I/A | V/VV / \text{V}V/V |
|---|---|
| 0.30 | 0.45 |
| 0.40 | 0.60 |
| 0.50 | 0.75 |
| 0.60 | 0.90 |
| 0.70 | 1.05 |
The measured length of wire YYY is l=25.0 cml = 25.0\text{ cm}l=25.0 cm.
Determine the gradient GGG of the graph of VVV against III.
Calculate the resistance per unit length RRR of wire YYY using the equation:
R=Gl R = \frac{G}{l} R=lGGive your value for RRR to a suitable number of significant figures and include the unit.
The student discovers that the resistance wire in the circuit control loop becomes very hot when the adjustable contact is connected to short lengths of the wire. Suggest one practical improvement that would help to reduce this effect.
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.