A student investigates the resistance of a resistance wire using a practical setup. Keeping the current in the circuit constant at I=0.40 AI = 0.40\text{ A}I=0.40 A, the student records the potential difference VVV across different lengths lll of the wire.
The student's readings are shown in the table below:
| l / cml\text{ / cm}l / cm | V / VV\text{ / V}V / V | Vl / (Vcm)\frac{V}{l}\text{ / }\left(\frac{\text{V}}{\text{cm}}\right)lV / (cmV) |
|---|---|---|
| 20.020.020.0 | 0.520.520.52 | |
| 40.040.040.0 | 1.041.041.04 | |
| 60.060.060.0 | 1.561.561.56 | |
| 80.080.080.0 | 2.082.082.08 | |
| 100.0100.0100.0 | 2.602.602.60 |
Complete the table by calculating and recording the values of Vl\frac{V}{l}lV to a consistent number of significant figures (2 or 3).
State your conclusion from these values of Vl\frac{V}{l}lV.
Justify your conclusion by referring to your calculated results.
Calculate the resistance RRR of the 100.0 cm100.0\text{ cm}100.0 cm length of the wire using the equation:
R=VI R = \frac{V}{I} R=IVwhere VVV is the potential difference across 100.0 cm100.0\text{ cm}100.0 cm of the wire. Give your answer to a suitable number of significant figures and include the correct unit.
Suggest one way to minimise the temperature rise of the resistance wire during this experiment.
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.