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x Standard Grade Physics > TELECOM Radio And Television > Flashcards

TELECOM Radio And Television Flashcards

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0
Q

What does the aerial do?

A

Picks up radio waves of different frequencies and converts them to electrical signals ( by vibrating when receiving radio waves which cause electrical charges) (picks up all of the radio signals)

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1
Q

What are the main parts of a radio receiver?

A

Aerial, tuner, decoder, amplifier, loudspeaker

                             power supply
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2
Q

What does the tuner do?

A

Selects one particular frequency from the received waves.

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3
Q

What does the decoder do?

A

Extracts the lower frequency audio signal from the transmitted higher frequency radio (carrier) signal

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4
Q

What does the amplifier do?

A

Increases the strength of the electrical signal

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5
Q

What does the loudspeaker do?

A

Converts the electrical energy to sound

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6
Q

What part of a radio receiver uses a power supply? Why?

A

Amplifier, i order to have energy to increase the wave siz

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7
Q

What is the difference between television parts and radio parts

A

There are two decoders and amplifiers; one of each for the audio waves and visual waves

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8
Q

What does a loudspeaker do in a television?

A

Converts electrical energy to sound

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9
Q

What does a picture tube do in a television?

A

Converts electrical signal to light

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10
Q

How is light formed on a television screen?

A

An electron gun fires a beam of electrons at the phosphor paint on the screen where the kinetic energy is then turned into a spot of light.

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11
Q

How are images built up on a television screen?

A

The electron gun fires electron beams across the screening a series of lines.

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12
Q

How many lines are on a television screen?

A

625

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13
Q

How are colours made on television screens?

A

Mixing light from red, green and blue electron guns.

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14
Q

What is amplitude modulation?

A

Varying the amplitude of a high frequency carrier wave so as to carry a low frequency audio wave

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15
Q

Carrier wave + audio signal —–>

A

amplitude modulated

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16
Q

Why would a wave be frequency modulated?

A

Better sound quality and method can be heard with no interference

17
Q

How are television signals transmitted?

A

Same as radio except thecRrier wave is modulated to carry two signals (audio and visual)

18
Q

How is brightness varied on a television screen?

A

By varying the number of electrons hitting the screen

19
Q

How often is a new picture produced?

A

25 times each second

20
Q

Why do television pictures move?

A

Due to image retention each image merges into the next. since each picture is only slightly different from the one before the images appear to move.

21
Q

How are colours other than the primary colours produced on a screen?

A

By mixing them

22
Q

Red + green

A

Yellow

23
Q

Red + blue

A

Magenta

24
Q

Blue + green

A

Cyan

25
Q

Red + green + blue

A

White

26
Q

How colours than primary and secondary colours made?

A

Varying the intensities (eg giving slightly more red to produce orange rather than yellow)

27
Q

Why are waves amplitude modulated?

A

So as to travel longer distances.

29
Q

The ____ frequency audio waves and ____ frequency audio signals are electrical signals,

A

High frequency radio (carrier), low frequency audio

30
Q

What are the parts of a radio transmitter?

A

Modulator, amplifier, aerial

31
Q

What does the modulator do in a radio transmitter ?

A

Combines the radio and audio signal

32
Q

What does the amplifier do in a radio transmitter

A

Makes the electrical signal arronger

33
Q

What does the aerial do in a radio transmitter

A

Changes electrical signals into radio waves and sends them out in all directions

34
Q

How to radio stations keep signals separated?

A

Transmitting in different wave lengths

35
Q

How would a diaphragm of a loudspeaker react for high pitch sounds?

A

Increased vibrates rapidly

36
Q

How is a louder sound produced in a loudspeaker?

A

Increasing the current rough the coil and vibrations of diaphragm are much larger

37
Q

What are used to direct and electron gun?

A

Magnetic coils

38
Q

Are electrons coloured to produce coloured images?

A

No, it is the material of the dots

39
Q

Why are waves amplitude modulated?

A

So they can travel longer distances

40
Q

Simply, how is a moving picture seen (3)

A

Line build up, image retention and brightness variation

52
Q

Why are more transmitters need for FM waves?

A

The do not travel as far as amplitude modulated waves

x Standard Grade Physics (29 decks)

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