The method and the results are on the ohm's law lab. Do the analysis yourself first, then check the answers below.
Quick answer: Current is the flow of charge in amperes, potential difference is the energy per coulomb in volts, and resistance in ohms is the opposition to current. These answers go with the Physics 9-10 lab on ohm's law: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
These model answers use the sample table. Your own values will differ because every thermistor has its own rating, but the curve should fall steeply at low temperature and flatten as the water gets hotter.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: GCSE P2, IGCSE 4.3
A falling curve: the points form a curve that falls steeply at low temperature and flattens at high temperature, from 12.5 kΩ at 20 °C to 1.76 kΩ at 70 °C.
Question 2 Describe the pattern
Resistance decreases as temperature rises. A thermistor with this behaviour is an NTC (negative temperature coefficient) thermistor.
5.0 kΩ lies between 5.30 kΩ (40 °C) and 3.59 kΩ (50 °C). Interpolating gives about 42 °C.
Question 5 Current in a circuit
20 °C: I = 6.0 ÷ 12540 = 0.48 mA. 70 °C: I = 6.0 ÷ 1760 = 3.41 mA.
Question 6 Sources of error
Temperature differs between the water and the thermistor because the glass delays the heat (thermal lag), and the thermometer is read only to 1 °C. The thermistor leads also add a small resistance.
Question 7 Improvement
Stir continuously and wait longer at each step so the thermistor reaches the water temperature; use a digital thermometer and repeat the cooling run to average the readings.
