Required Practical: Investigating Resistance Flashcards
All 6 cards in this deck
What are the steps to investigate how the resistance of a wire depends on its length?
e.g. lengths from 10 cm to 100 cm- Connect the test wire in series with a cell, switch and ammeter, with a voltmeter across the wire.
- For each length, close the switch briefly, record and , and calculate .
- Plot resistance against length — a straight line through the origin.
How does the resistance of a wire depend on its length at constant temperature?
Resistance is directly proportional to length — a straight line through the origin on a resistance–length graph.
Why is the switch only closed briefly for each reading in the resistance-of-a-wire practical?
To stop the wire heating up, so the temperature stays constant.
Which variables must be controlled when investigating how a wire's resistance depends on its length?
The material and thickness (cross-sectional area) of the wire, the supply pd, and the temperature of the wire.
What is a zero error on an ammeter?
The meter reads a value other than zero when there is no current, so every reading is out by that amount.
True or false? A 1.5 V cell is an electrical hazard to the student in the resistance-of-a-wire practical.
False. The potential difference is very low, so there is no risk of electric shock.