Electromagnetism Flashcards
1
Q
Radio waves wavelength
A
1m
2
Q
Microwaves wav length
A
1cm
3
Q
Infared wavelength range
A
1mm
4
Q
Visable wavelength range
A
500nm
5
Q
Uv wavelength range
A
100nm
6
Q
X-rays wavelength range
A
10nm
7
Q
Gamma rays wavelength range
A
Less than 1nm
8
Q
Radio waves frequency range
A
3-10Hz^9
9
Q
Microwaves frequency range
A
1-300Hz ^9
10
Q
Infared frequency range
A
3-4000Hz^11
11
Q
Visablelight frequency range
A
4-8Hz^14
12
Q
Uv frequency range
A
8-30Hz^16
13
Q
X-rays frequency
A
3-3000hz^16
14
Q
Gamma ray frequency
A
10^19Hz
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
16
Q
Uses of radio waves
A
-telecommunications
17
Q
Dangers of radio waves
A
- very high rf intensity- heating and burns of biological tissue
- large does can cause cancer
18
Q
Microwaves source
A
-produced inside microwave oven by an electron tube called a magnetron- microwaves are reflected within the oven
19
Q
Uses of microwaves
A
- food
- telecommunications - short range
20
Q
Dangers of microwaves
A
Burning
21
Q
Infared radiation sources
A
-emmitted from heated surfaces
22
Q
Uses of infared
A
-heating- toaster
23
Q
Danegrs of infared
A
Burns
24
Q
Visable light source
A
- the sun
- light bulbs
25
Uses of visable light
- vision- eye sight
| - photography
26
Dangers of visable light
-blindness if intense in direct source
27
Uv source
Sun light
28
Uses uv
Sterilisation
29
Uv dangrs
Ionising- cancer
30
X-rays sources
- 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
X-rays uses
Diagnosis
32
X-rays dangers
Ionising- cancer
33
Gamma rays sources
- relased during nuclear fission or radioactive decay
| - eg. Nucleur explosions, lightnig, black holes, neutron stars
34
Gamma rays uses
Radiotherapy
35
Gamma rays dangers
Ionising- cancer
36
Magnetic north pole
North seeking pole, region at end of magnet were external magnetic field is strongest
37
Magnetic field lines
- shows direction felt by N pole
| - more dense lines, stronger the force
38
Current around wire
- 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
Force on charged particles
- 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
current direction
Flow of positive charge
41
Syncotron
- aim electrons pass around large circular building
| - uses magnets to bend in certain directions
42
Mass spectrometer
- 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
Solenoid
- coil of wire
- can have holloe or iron/steel core
- current flowing through wire, produces uniform magnetic field through it
44
Factors which affect strength of solenoid
- no. Turns- more, stronger
- current flowing through it
- shape electromagnet
- presence iron core- increases strength
45
Motor effect
- 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
Dc motor
- 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
Factors affecting motor speed
- 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
Electromagnetic induction
- wire moved through magnetic field produces an emf
| - if wire forms a circuit-current is produced
49
Generator effect
Right hand rule
50
Lenz law
Induced current flows so as to oppose th motion that made it
51
Faradays law
EMF enduced proportionally to rate that field lines are cut
52
Ac generator
- 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
When coil parallel to magnetic field- ac generator
-large current/emf
54
When coil perpendicular to magnet- ac generator
-no current
55
Ac electrons
-vibrating back and forth
56
Voltage mains pd
230V
57
Frequency mains
50Hz
58
Ways to increase voltage produced- ac
- turn coil more rapidly
- use coil w/more turns
- coil bigger are
- use stronger magnets
