Which variables must be kept the same in an investigation of how the current in a fixed resistor varies with potential difference?

The same resistor must be used throughout and its temperature must be kept constant.

What is the shape of the graph of current against potential difference for a fixed resistor kept at constant temperature?

It is a straight line through the origin, showing that the current is directly proportional to the potential difference.

What does a straight-line graph of current against potential difference tell you about the resistance of a fixed resistor?

The resistance stays constant, because the ratio of potential difference to current is the same at every point.

What is the shape of the graph of current against potential difference for a filament lamp?

It is a curve that becomes less steep as the potential difference increases.

Edexcel GCSE Physics 1PH0

Key Concepts of Physics

Topic overview SI units in physics Multiples and sub-multiples of units Converting units, significant figures and standard form

Motion and Forces

Topic overview Scalar and vector quantities Examples of vectors and scalars, and velocity Speed, distance, time and distance-time graphs Acceleration and the equation v squared minus u squared Velocity-time graphs and free fall Measuring speed in the laboratory, and typical everyday speeds Newton's first law, and investigating force, mass and acceleration Newton's second and third laws Weight, mass and gravitational field strength Reaction time, stopping distance and large decelerations Factors affecting stopping distance and reaction time Braking distance, speed and work done

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Astronomy

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Electricity and Circuits

Static Electricity

Topic overview Charging by friction, and attraction and repulsion Electrostatic phenomena and earthing Uses and dangers of static electricity Electric fields

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Electromagnetic Induction

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Electricity and Circuits

Investigating resistance in circuits

2 things to know
Paper 2

Overview

The circuit for a fixed resistor, the variables changed, measured and controlled, the straight-line and curved graphs for a resistor and a filament lamp, and results for series and parallel combinations.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What circuit is used to investigate how the current in a fixed resistor depends on the potential difference across it?

Key term

In an investigation of how current depends on potential difference for a fixed resistor, which quantity is changed and which quantities are measured?

Questions from this subtopic

Each one with the model answer underneath.

1
What circuit is used to investigate how the current in a fixed resistor depends on the potential difference across it?
Model answer
A cell, a switch, a variable resistor and the fixed resistor are joined in series with an ammeter, and a voltmeter is connected across the resistor.
2
In an investigation of how current depends on potential difference for a fixed resistor, which quantity is changed and which quantities are measured?
Model answer
The potential difference is changed using a variable resistor, and both the current and the potential difference are measured.
3
Which variables must be kept the same in an investigation of how the current in a fixed resistor varies with potential difference?
Model answer
The same resistor must be used throughout and its temperature must be kept constant.
4
What is the shape of the graph of current against potential difference for a fixed resistor kept at constant temperature?
Model answer
It is a straight line through the origin, showing that the current is directly proportional to the potential difference.
5
What does a straight-line graph of current against potential difference tell you about the resistance of a fixed resistor?
Model answer
The resistance stays constant, because the ratio of potential difference to current is the same at every point.
6
What is the shape of the graph of current against potential difference for a filament lamp?
Model answer
It is a curve that becomes less steep as the potential difference increases.

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