Power, Current and Voltage (1 Viewer)

[weirdguy99]

Hey,

I've recently been having trouble with connecting the dots between power, current, voltage, coulombs and energy.

Been going through the textbooks but I need a deeper look into these units.

So far I understand that an Amp is the measure of coulombs and that voltage is the force that drives the Amp's through a closed circuit....

Could someone please help clarify them?

Thanks.

 

[darkchild69]

Power: Measured in Watts, which equivalent unit is Joules/sec. It is the rate at which energy is used. Example a 100W device uses 100J of Energy per second.

Current: Measured in Amperes, it's equivalent unit is Coulombs/second. It is the rate at which charge flows past a certain point. A current of 2A is equivalent to a charge of 2 Coloumbs passing a point each second.

Voltage: aka Potential Difference or Electromotive Force (EMF). It is measured in Volts, an the equivalent unit is energy per unit charge (Joules/Coulomb). Basically, the higher the EMF, the more electrical potential energy each charge will gain. Voltage is a measure of the work which is needed to be done by a charge moving from one point to another.

Coulombs: The unit for charge. Not much more to say about it 1 coulomb is the equivalent charge of a current of 1A flowing for 1second. 1 coloumb is the charge on 6.242 × 10¹⁸ electrons.

Energy: Unit is Joules. Can be defined in a number of ways Energy and Work have equivalent units.
Most commonly used: 1 Joule is the work required to produce a Watt of power for 1 second (Eg, using a 100W bulb for 5 seconds generates 500J of Energy)
Others:
The work required to move a charge of 1 coulomb through a PD of 1 volt or the work done by a force of 1 Newton moving an object a distance of 1 metre.

Hope this helps

 

[weirdguy99]

Hey, thanks for the reply.

If voltage rises and resistance is the same, does that mean the current will rise? since each charge gains more potential energy.

 

[untouchablecuz]

Hey, thanks for the reply.

If voltage rises and resistance is the same, does that mean the current will rise? since each charge gains more potential energy.

V=I*R

if R is constant, then, V is proportional to I

if V increases then, because V and I are proportional, I will also rise

 

[weirdguy99]

Yep, thats what I thought.

Appreciate your help guys =)

 

[alcalder]

I = current in amperes (A)
q = charge in coulombs (C)
n = no. of electrons
e = electrical charge of one electron in coulombs (C)
t = time in seconds (s)
V = voltage in voltes (V)
R = resistance in ohms (sigma)
p (rho) = constant proportionality resistivity of a metal (in ohm metres)
l = length in metres (m)
A = cross sectional area of a wire in metres squared
P = power in watts (W)
W = work in joules (J)
r = internal resistance of a battery (in ohms)

I = q/t

I = nev

EMF = energy supplied/q
Energy released = V x q
W = Vq

R = V/I
or V = IR

R = pl/A

P = W/t
P = VI
P = V²/R
P = I²R

EMF supplied = I (r + R)

Just to help put them all into equations for you.