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Physics > Electromagnetism > Flashcards

Electromagnetism Flashcards

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1
Q

Radio waves wavelength

A

1m

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2
Q

Microwaves wav length

A

1cm

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3
Q

Infared wavelength range

A

1mm

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4
Q

Visable wavelength range

A

500nm

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5
Q

Uv wavelength range

A

100nm

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6
Q

X-rays wavelength range

A

10nm

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7
Q

Gamma rays wavelength range

A

Less than 1nm

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8
Q

Radio waves frequency range

A

3-10Hz^9

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9
Q

Microwaves frequency range

A

1-300Hz ^9

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10
Q

Infared frequency range

A

3-4000Hz^11

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11
Q

Visablelight frequency range

A

4-8Hz^14

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12
Q

Uv frequency range

A

8-30Hz^16

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13
Q

X-rays frequency

A

3-3000hz^16

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14
Q

Gamma ray frequency

A

10^19Hz

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15
Q

Radio waves source

A
  • natural sources-lighting, astronomical phenomena
  • artificial sources- broadcast radio towers, sattelite,radar, cell phones
  • can be produced by oscillations in electrical circuits when aborbed by a conductor creates ac- has same frquency as radio waves
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16
Q

Uses of radio waves

A

-telecommunications

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17
Q

Dangers of radio waves

A
  • very high rf intensity- heating and burns of biological tissue
  • large does can cause cancer
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18
Q

Microwaves source

A

-produced inside microwave oven by an electron tube called a magnetron- microwaves are reflected within the oven

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19
Q

Uses of microwaves

A
  • food

- telecommunications - short range

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20
Q

Dangers of microwaves

A

Burning

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21
Q

Infared radiation sources

A

-emmitted from heated surfaces

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22
Q

Uses of infared

A

-heating- toaster

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23
Q

Danegrs of infared

A

Burns

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24
Q

Visable light source

A
  • the sun

- light bulbs

25
Q

Uses of visable light

A
  • vision- eye sight

- photography

26
Q

Dangers of visable light

A

-blindness if intense in direct source

27
Q

Uv source

A

Sun light

28
Q

Uses uv

A

Sterilisation

29
Q

Uv dangrs

A

Ionising- cancer

30
Q

X-rays sources

A
  • natural sources- radioactive elements, cosmic rays
  • man made- accelerating eletrons through a pd, directing onto target material, electrons release x-rays as slow down in target
31
Q

X-rays uses

A

Diagnosis

32
Q

X-rays dangers

A

Ionising- cancer

33
Q

Gamma rays sources

A
  • relased during nuclear fission or radioactive decay

- eg. Nucleur explosions, lightnig, black holes, neutron stars

34
Q

Gamma rays uses

A

Radiotherapy

35
Q

Gamma rays dangers

A

Ionising- cancer

36
Q

Magnetic north pole

A

North seeking pole, region at end of magnet were external magnetic field is strongest

37
Q

Magnetic field lines

A
  • shows direction felt by N pole

- more dense lines, stronger the force

38
Q

Current around wire

A
  • right thumb rile
  • electric current generates magnetic field
  • strength proportional to current
  • concentric circles around wire
  • field is weaker (less dense) further away from wire
39
Q

Force on charged particles

A
  • any moving charge produces a magnetic field around it
  • in magnetic field- electron passes through uniform magnetic field
    • feels force due to interacting fields(lhr)
    • cause perpendicular force-circular motion
40
Q

current direction

A

Flow of positive charge

41
Q

Syncotron

A
  • aim electrons pass around large circular building

- uses magnets to bend in certain directions

42
Q

Mass spectrometer

A
  • find mass of atom
  • ionise atom
  • propel by passing through magnetic field towards detector
  • if accelerate less, larger mass- position on detector determines mass
43
Q

Solenoid

A
  • coil of wire
  • can have holloe or iron/steel core
  • current flowing through wire, produces uniform magnetic field through it
44
Q

Factors which affect strength of solenoid

A
  • no. Turns- more, stronger
  • current flowing through it
  • shape electromagnet
  • presence iron core- increases strength
45
Q

Motor effect

A
  • two magnetic fields interacting to create force of repulsion
  • current carrying wire produces a magntic field, placed inside external magnetic field (two permenant magnets) experiencing a force
46
Q

Dc motor

A
  • split ring commutator
  • current in wire produces magnetic field, interacts w/ uniform field
    • causing force LHR- coil rotates
  • when coil parallel magnets
    • no current flows, still spins due to momentum
  • when passes other pole of magnet, reverse current -force felt same direction
47
Q

Factors affecting motor speed

A
  • higher current- faster rotation
    • stronger electromagnetic force
  • stronger uniform field, faster rotaion
    • more interaction
  • more turns-faster rotation
    • strongr magnetic force, more field lines cut
48
Q

Electromagnetic induction

A
  • wire moved through magnetic field produces an emf

- if wire forms a circuit-current is produced

49
Q

Generator effect

A

Right hand rule

50
Q

Lenz law

A

Induced current flows so as to oppose th motion that made it

51
Q

Faradays law

A

EMF enduced proportionally to rate that field lines are cut

52
Q

Ac generator

A
  • slip ring commutator
  • as coil rotates, each side of coil passes diff side magnetic pole
    • coil spin magnetic field, current induced
  • induced current changes direction- ac
53
Q

When coil parallel to magnetic field- ac generator

A

-large current/emf

54
Q

When coil perpendicular to magnet- ac generator

A

-no current

55
Q

Ac electrons

A

-vibrating back and forth

56
Q

Voltage mains pd

A

230V

57
Q

Frequency mains

A

50Hz

58
Q

Ways to increase voltage produced- ac

A
  • turn coil more rapidly
  • use coil w/more turns
  • coil bigger are
  • use stronger magnets

Physics (8 decks)

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