Which of the live and neutral wires is dangerous to touch, and why?

The live wire, because it is at about 230 V while a person standing on the ground is at 0 V.

What colour is the insulation on the live wire and on the neutral wire in a mains plug?

The live wire is brown and the neutral wire is blue.

Why is the neutral wire much safer to touch than the live wire, even though the current in both is the same?

The neutral wire stays close to 0 V, so there is almost no potential difference between it and a person standing on the ground.

In an appliance that is working normally, how do the currents in the live and neutral wires compare?

They are equal, because the charge that flows in through one wire flows back out through the other.

Edexcel GCSE Combined Science Physics 1SC0

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

Conservation of Energy

Topic overview Gravitational potential and kinetic energy Energy transfer diagrams and conservation of energy Energy stores and closed systems Dissipation and wasteful energy transfer Reducing unwanted energy transfer Calculating efficiency Energy resources and trends in their use

Waves

Topic overview What waves transfer, and the evidence for it Frequency, wavelength, amplitude and period Longitudinal and transverse waves The wave equation Measuring wave speed, and what happens at a boundary Measuring waves in ripple tanks, strings and solids

Light and the Electromagnetic Spectrum

Topic overview Properties of electromagnetic waves Investigating refraction in glass blocks The groups of the electromagnetic spectrum The continuous spectrum, and what our eyes can detect How radiation is generated, and why danger rises with frequency Harmful effects of excessive exposure to radiation Uses of electromagnetic radiation

Radioactivity

Topic overview The atom and the size of atoms Isotopes, atomic number and mass number Relative masses and charges of subatomic particles Electron orbits and energy levels Forming ions, and how the atomic model changed Types of ionising radiation Background radiation and detecting radioactivity Alpha, beta and gamma, and their penetrating power Beta-minus and beta-plus decay Effects of decay on atomic number and mass number Balancing nuclear equations Activity and the becquerel Half-life and the randomness of decay Half-life calculations The dangers of ionising radiation Safety precautions, contamination and irradiation

Energy – Forces Doing Work

Topic overview Energy stores and energy transfer diagrams Changing a system's energy, and measuring work done Work done and the energy changes it causes Gravitational potential and kinetic energy calculations Dissipation and wasted energy Power as the rate of energy transfer The watt, and calculating efficiency

Forces and Their Effects

Topic overview Contact and non-contact forces Vectors and scalars, and reducing friction

Electricity and Circuits

Magnetism and the Motor Effect

Topic overview Magnetic poles, permanent and induced magnets Uses of magnetic materials The magnetic field around a bar magnet Plotting compasses and the Earth's magnetic field The magnetic effect of an electric current Solenoids and electromagnets

Electromagnetic Induction

Topic overview The national grid, and step-up and step-down transformers Transformer power calculations

Particle Model

Topic overview Kinetic theory and differences in density Calculating density, and investigating it Changes of state and internal energy Specific heat capacity Specific latent heat and thermal insulation Investigating the specific heat capacity of water Gas pressure and the motion of particles Absolute zero and the kelvin scale

Forces and Matter

Topic overview Elastic and inelastic distortion Spring constant, and linear and non-linear behaviour Work done in stretching a spring

Electricity and Circuits

Live and neutral wires, earthing and fuses

2 things to know
Paper 6

Overview

The functions and colours of the live, neutral and earth wires, why the live wire is dangerous, equal currents in live and neutral, earthing a metal case, how fuses and circuit breakers protect a circuit, and choosing a fuse rating.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is the function of the live wire in a mains circuit?

Key term

What is the function of the neutral wire in a mains circuit?

Questions from this subtopic

Each one with the model answer underneath.

1
What is the function of the live wire in a mains circuit?
Model answer
The live wire carries the alternating potential difference from the supply to the appliance.
2
What is the function of the neutral wire in a mains circuit?
Model answer
The neutral wire completes the circuit by carrying the current back to the supply.
3
Which of the live and neutral wires is dangerous to touch, and why?
Model answer
The live wire, because it is at about 230 V while a person standing on the ground is at 0 V.
4
What colour is the insulation on the live wire and on the neutral wire in a mains plug?
Model answer
The live wire is brown and the neutral wire is blue.
5
Why is the neutral wire much safer to touch than the live wire, even though the current in both is the same?
Model answer
The neutral wire stays close to 0 V, so there is almost no potential difference between it and a person standing on the ground.
6
In an appliance that is working normally, how do the currents in the live and neutral wires compare?
Model answer
They are equal, because the charge that flows in through one wire flows back out through the other.

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