emf/current (1 Viewer)

[zenger69]

there was a question we had for a motors and generators topic test. It was fill in the blanks. The change in magnetic flux induces a/an ___________ in the coil.

So I wrote current.

But my teacher said should be an electromagnet force (emf) but aren't they the same thing. If emf is measured in V and Current measured in I.

P=VI therefore if there's voltage there's a current.

therefore they are ultimately the same thing, they are power.

Is that true what i've said or wrong?

 

[AntiHyper]

it should be the change in flux over change in time equals emf:
EMF = ^{change in flux}/_{change in time}

 

[MuffinMan]

For a current to flow through a galvanometer, there must be an emf.
So it should be like this shouldnt it

The change in magnetic flux induces a/an emf in the coil which produces a current
by the way emf = electromotive force not electromagnet force
hope this helps
ps i just had my physics half yearly today...didnt feel like to talk about physics anymore...

 

[Will Hunting]

there was a question we had for a motors and generators topic test. It was fill in the blanks. The change in magnetic flux induces a/an ___________ in the coil.

So I wrote current.

But my teacher said should be an electromagnet force (emf) but aren't they the same thing. If emf is measured in V and Current measured in I.

P=VI therefore if there's voltage there's a current.

therefore they are ultimately the same thing, they are power.

Is that true what i've said or wrong?

Nah, dude.

Moving a magnetic field relative to a conductor, or changing magnetic flux, induces a potential difference across ends of the conductor. This supplies charges, in the conductor, with potential energy, the induced potential difference resulting in work done on the charges and the conversion of (electrical) potential energy into kinetic energy i.e. a current will flow. This is what emf is, man. It's defined as energy supplied/charge and refers to the energy possessed by charges due to a P.D. across a source, in this case, the P.D. induced in the conductor by the change in flux.

Don't confuse emf with current. They are both related but are still distinguishble as entities in their own rights. Power is a dimension derived from the two "separate" dimensions, V and I. Don't mix power up with emf either.

 

[zenger69]

so when should i use the term Current and when should I use the term EMF?

 

[Will Hunting]

In the case of elecromagnetic induction,

You should say: an emf has been induced across ends of the conductor
And you should say: By Lenz' Law, current will flow in the direction such to oppose the change in magnetic flux that caused the induced emf

Note that, qualitatively, emf and current are "equivalent", but not the same thing. You cannot induce an emf without causing current to flow, and, conversely, a current cannot exist without an emf, but they are, technically, different things measured in different units and representing different activities (on the subatomic scale)

 

[zenger69]

ok.. thanks heaps.