A student is investigating how the resistance of a filament lamp changes with potential difference. They record the current III through the lamp for several potential difference VVV values, obtaining the following data:
| VVV (V) | III (A) |
|---|---|
| 1.5 | 0.24 |
| 3.0 | 0.40 |
| 4.5 | 0.50 |
| 6.0 | 0.58 |
| 7.5 | 0.64 |
Calculate the resistance RRR (in Ω\OmegaΩ) of the lamp for each potential difference value using the formula R=VIR = \frac{V}{I}R=IV. Record all values to 2 significant figures.
State the trend in the resistance of the lamp as the potential difference increases, and briefly explain this trend in terms of the behavior of the filament.
In a modified version of this experiment, the potential divider arrangement is replaced. State the standard circuit symbol for a variable resistor (rheostat) and state whether it should be connected in series or parallel with the lamp to change the current through it.
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.