Express the volt in SI Base Units

Can anyone tell me what the answer is, this question was just in my AS physics exam:

Express the volt in terms of the SI base units: kg, m, s and A

kg m² s^-3 A^-1

Ok, any chance you could put the working of that up?? Thanks :smile:

Reply 3

teachercol

Volts = Joules / Coulombs

Joules = Newton x metre

Coulomb = Amp * second (edit oops)

Newton = kg x metre / second squared

Put it all together.

Reply 4

Knogle

Voltage = Power/Current
Power = Energy/Time (Joules/second)
Energy = Force * Distance
Force = Mass * Acceleration (Newton's 2nd law)

=> SI base units of Force: kg m s^-2
=> SI base units of Energy: kg m² s^-2
=> SI base units of Power: kg m² s^-3
=> SI base units of Voltage: kg m² s^-3 A^-1

Thanks!!

Bitteschon. :gthumb:

hey, isn't the charge a more 'base' unit than current?
in which case it would be N m C^-1

Reply 8

Mehh

john-boro

hey, isn't the charge a more 'base' unit than current?
in which case it would be N m C^-1

Not in SI it seems. On top of those above there is also the Kelvin Candela and Mole.
Its actually quite logical. The Ampere predated the Coulomb.

Reply 9

forkwise

Yes, but I think he meant that current is the rate of flow of charge, (Q/t) so one would assume that charge should be the base unit. I know it's not :p:

Reply 10

john-boro

Having said that, charge was defined to me as 'one coulomb is the charge that is transferred when one amp flows for one second'. So I guess you're right, Amperes are the 'first' unit and so the SI one. It just seems weird because usually things are not defined as a product of time and another thing. Like a metre isn't defined as the distance moved when something going 1m/s moves for 1 s. Or maybe it is :p: