What is meant by calling a circuit element non-linear?

The current through it is not proportional to the potential difference across it, so its graph of current against potential difference is a curve rather than a straight line.

A component gives 0.4 A at 2 V, 0.8 A at 4 V and 1.2 A at 6 V. Is it linear or non-linear, and what is its resistance?

It is linear, and its resistance is a constant 5 Ω.

A component gives 0.5 A at 1 V, 0.8 A at 2 V and 1.0 A at 3 V. Is it linear or non-linear, and what is happening to its resistance?

It is non-linear, and its resistance is rising, from 2 Ω to 2.5 Ω and then to 3 Ω.

Two components each give a straight line through the origin on the same axes of current against potential difference, and one line is steeper. What does the steeper line tell you?

That component has the lower resistance, because it carries more current for the same potential difference.

OCR GCSE Combined Science Physics J250

Electricity

Topic overview Charge, and producing static electricity Transfer of electrons in charging and discharging Current as a rate of flow of charge Charge, current and time Series and parallel circuits, and circuit symbols Current, potential difference and resistance Resistors whose resistance changes, and investigating them Linear and non-linear circuit elements from graphs Net resistance in series and parallel Circuits for measurement, and electrical power

Energy

Topic overview Conservation of energy, and energy stores Energy changes on heating, and calculating them Energy of a moving body, a spring and a raised object Dissipation, and energy transfer in domestic devices Power ratings, efficiency, and increasing it Reducing unwanted energy transfer, and the rate of cooling

Forces

Global Challenges

Topic overview Typical speeds and everyday accelerations Reaction time, stopping distance and the dangers of large decelerations Stopping distance, acceleration and collision force calculations Energy resources, and trends in their use The national grid, and step-up and step-down transformers Why the national grid is efficient, and power in a transformer Mains electricity: a.c., d.c. and the domestic supply Live, neutral and earth wires, and electrical danger

Magnetism and Magnetic Fields

Topic overview Permanent and induced magnets, and magnetic poles Magnetic fields, and the dipping compass The magnetic effect of a current, and solenoids The motor effect and Fleming's left-hand rule The force on a conductor, and how a motor turns

Matter

Topic overview How the atomic model changed, and the structure of the atom The size of atoms, and defining density Density of the states of matter, and density calculations Conservation of mass in changes of state Heating a system, and specific heat capacity Calculations with specific heat capacity and latent heat Gas molecules, temperature and pressure

Radioactivity

Topic overview Protons, neutrons and isotopes Unstable nuclei and the emissions they give out Balancing nuclear equations Electron energy levels, and radiation from atoms Half-life and the randomness of decay Penetration of alpha, beta and gamma Contamination and irradiation, and reducing the hazard

Waves in Matter

Topic overview Amplitude, wavelength, frequency and period The wave equation Transverse and longitudinal waves Modelling waves with ripples and sound Electromagnetic waves as transverse, and energy transfer Frequency and wavelength across the spectrum What our eyes detect, and light as an electromagnetic wave Uses of electromagnetic waves Hazards of ultraviolet, X-rays and gamma rays Producing and receiving radio waves Absorption, transmission, refraction and reflection Investigating reflection and refraction of light

Electricity

Linear and non-linear circuit elements from graphs

3 things to know
Paper 11 (Physics)

Overview

Straight and curved graphs of current against potential difference, finding resistance from readings and from a graph, the characteristic graphs of a fixed resistor, a filament lamp and a diode, resistance graphs for a thermistor and a light dependent resistor, and plotting results with y = mx + c and a line of best fit.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Compare the current against potential difference graphs of a fixed resistor and a filament lamp, and explain their shapes.

Key term

What shape is the graph of current against potential difference for a linear circuit element?

Key term

Why does a straight line through the origin on a current against potential difference graph show that the resistance is constant?

Questions from this subtopic

Each one with the model answer underneath.

1
What shape is the graph of current against potential difference for a linear circuit element?
Model answer
A straight line passing through the origin.
2
What is meant by calling a circuit element non-linear?
Model answer
The current through it is not proportional to the potential difference across it, so its graph of current against potential difference is a curve rather than a straight line.
3
A component gives 0.4 A at 2 V, 0.8 A at 4 V and 1.2 A at 6 V. Is it linear or non-linear, and what is its resistance?
Model answer
It is linear, and its resistance is a constant 5 Ω.
4
A component gives 0.5 A at 1 V, 0.8 A at 2 V and 1.0 A at 3 V. Is it linear or non-linear, and what is happening to its resistance?
Model answer
It is non-linear, and its resistance is rising, from 2 Ω to 2.5 Ω and then to 3 Ω.
5
Why does a straight line through the origin on a current against potential difference graph show that the resistance is constant?
Model answer
The potential difference divided by the current gives the same value at every point on such a line.
6
Two components each give a straight line through the origin on the same axes of current against potential difference, and one line is steeper. What does the steeper line tell you?
Model answer
That component has the lower resistance, because it carries more current for the same potential difference.

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