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With 'u' (unified mass unit) what do we need to know?
I mean are we told what the masses of things are in terms of u, or do we need to know, say, the mass of a proton in u (all i know is that its about 1)
And why can't you just times the mass of an electron by 1860?
Urgh!
If we need to know certain values, could someone be lovely and post a list??
xxxx
Reply 21
1u = 1.66 x 10^-27 kg

1eV = 1.6 X 10^-19 J

1u = 931.5 MeV
Reply 22
To convert from joules to electrovolt DIVIDE by 1.6 x 10^-19
Reply 23
can someone explain potentiometers to me?
Reply 24
Kashya
Okay..this might be a bit late as the test is in less than 12 hours but I thought Id compile a short list of order's of magnitude of some physical quanitites that apparantely we should know for our specification:

Please if you know any more we should know, post and let us know!

Okay:

Size of an atom:
10^-10m
Size of an atomic nucleus: 10^-14m
Typical carrier drift speeds in metals: 0.02mm/s for electrons in a conductor.
Wavelength of the EM:

1.

Gamma Rays- 10^-12m

2.

Xrays- 10^-10m

3.

UV- <400nm

4.

Visible light- 700-400nm

5.

Infra-red- 1^-6m

6.

Microwaves- 10cm (Ive been told it was 3cm however..?)

7.

Radiowaves- These can range from 1m to 1200m depending on the type


Typical dimensions for a double-slit interference experiment: 0.5mm slit width. 1-2m distance from screen
Typical density of some solids, gases and liquids:

Iron 8000 kg/m^3

Water 1000kg/m^3

Wood (oak) 700kg/m^3

Air 1.3kg/m^3


Atmospheric Pressure:: 101kPa
Speed of sound: 330m/s to 340m/s

Remember Kelvin temperature too. Kelvin temp= Celsius temp + 273


Specific Heat Capacity of water 4200 J / Kg K
~Adel~
Depends on the direction of the magnetic field. Remember that the direction of the particle will imply the direction of current. If it's a positive particle, the direction of movement will indicate the direction of current, if it's a negative particle, i.e; an electron, the current is opposite of the direction it travels.


yea kanyee,flemming's left hand rule don't detect the positive or negative charges it was detects the direction of current.
Reply 26
Just to note Ive just read:

Negative particles will produce a clock-wise spiral shape.
Positive particles will produce a anticlock-wise spiral shape.

Also, always remember when drawing the path of a particle through an electric field i.e. between two plates, TAKE NOTE OF THE PARTICLE. I dont know how many times Ive seen people use skim over say the fact that it was an electron and screwed the question up.

Also, the electric field direction is given by which way a positive point charge would move in that field.
Reply 27
anyone know how/what potentiometers work/do?
pico came up in a past paper i did (10^-12)
any idea how far we need to learn factors????

Here are some just in case:

Tera T 10^12
Giga G 10^9
Mega M 10^6
Kilo k 10^3
milli m 10^-3
micro (mu) 10^-6
nano n 10^-9
pico p 10^-12

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