How are radio waves produced?

By making charges oscillate in an electrical circuit connected to an aerial.

How does the frequency of the current induced in an aerial compare with the frequency of the radio wave that produced it?

It is the same as the frequency of the radio wave.

How does a radio receiver pick out one station from all the signals reaching its aerial?

Its circuit is tuned so that it oscillates strongly only at the frequency of that station.

Why is an aerial needed at both the transmitter and the receiver?

The transmitting aerial turns an oscillating current into radio waves and the receiving aerial turns the radio waves back into an oscillating current.

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

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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

Waves in Matter

Producing and receiving radio waves

3 things to know
Paper 12 (Physics)

Overview

How oscillating charges in a circuit and aerial produce radio waves, how an arriving wave induces an alternating current of the same frequency, tuning a receiver to one station, the energy transferred on reception, and why radio waves need no material between transmitter and receiver.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What happens in an aerial when a radio wave arrives at it?

Key term

Describe the energy transfer that takes place when a radio signal is received.

Key term

What has to change in a transmitting circuit to produce radio waves of a higher frequency?

Questions from this subtopic

Each one with the model answer underneath.

1
How are radio waves produced?
Model answer
By making charges oscillate in an electrical circuit connected to an aerial.
2
What happens in an aerial when a radio wave arrives at it?
Model answer
The wave makes the electrons in the aerial oscillate, which produces an alternating current in the circuit.
3
How does the frequency of the current induced in an aerial compare with the frequency of the radio wave that produced it?
Model answer
It is the same as the frequency of the radio wave.
4
How does a radio receiver pick out one station from all the signals reaching its aerial?
Model answer
Its circuit is tuned so that it oscillates strongly only at the frequency of that station.
5
Why is an aerial needed at both the transmitter and the receiver?
Model answer
The transmitting aerial turns an oscillating current into radio waves and the receiving aerial turns the radio waves back into an oscillating current.
6
Describe the energy transfer that takes place when a radio signal is received.
Model answer
Energy carried by the radio wave is transferred to the electrons in the aerial and appears as an electrical signal.

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