I-V Characteristics and Sensors

IGCSE Edexcel Physics
2.9-2.12 I-V Characteristics and Sensors
Key Concepts: Different components have different I-V graphs. LDR and thermistor resistance changes with light or temperature.

Section A: I-V Characteristics

1. Describe the I-V graph of a resistor. [2]
2. Describe the I-V graph of a filament lamp. [2]
3. Describe the I-V graph of a diode. [2]

Section B: Sensors

4. State what happens to LDR resistance when light intensity increases. [2]
5. State what happens to thermistor resistance when temperature increases. [2]
6. Explain why the I-V graph of a filament lamp curves as current increases. [2]
7. Suggest how an LDR is used in a street light circuit. [3]
Total marks: 15

Mark Scheme

1. Straight line through origin, constant resistance [2]
2. Curve that becomes less steep as voltage increases [2]
3. Little current until threshold, then current increases in one direction only [2]
4. Resistance decreases [2]
5. Resistance decreases (NTC) [2]
6. Filament heats up, resistance increases, so current increases less for each extra volt [2]
7. LDR has high resistance in the dark so lamp switches on; low resistance in daylight so lamp off (any clear control explanation) [3]