TrueTears question thread

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Why is it that when a coil spins faster in a generator, the emf is larger?

Can you apply emf = Blv in this case? (Coz I thought Blv is only used in situations where you have a rod and it's falling through a magnetic field, in this case its a coil that's rotating so...)

Thanks

If the wire is spinning faster, then the same will be covered in a shorter , so the emf is greater.

Also with I have a hunch that the formula still works for rotating wires, but not 100% sure

[TrueTears]

Why is it that when a coil spins faster in a generator, the emf is larger?

Can you apply emf = Blv in this case? (Coz I thought Blv is only used in situations where you have a rod and it's falling through a magnetic field, in this case its a coil that's rotating so...)

Thanks

If the wire is spinning faster, then the same will be covered in a shorter , so the emf is greater.

Also with I have a hunch that the formula still works for rotating wires, but not 100% sure

How would you prove emf = Blv still works?

[TrueTears]

1. Why is it that when a coil spins faster in a generator, the emf is larger?

Can you apply emf = Blv in this case? (Coz I thought Blv is only used in situations where you have a rod and it's falling through a magnetic field, in this case its a coil that's rotating so...)

2. If a generator produces AC current then does this imply that the voltage is AC voltage?

3. Why does a DC motor contain DC current? The current is reversed each half turn by a split ring commutator, so doesn't that become AC current?

Is it because the terminals of the battery doesn't change (unlike generators), it is just the split rings which attach themselves alternatively to the 2 terminals of the battery hence the current is still DC but the it is just "manipulated" to reverse at each half turn?

4. Describe the function performed by a commutator in a DC generator.

I thought commutators are only used in DC motors???

[james23]

4. Describe the function performed by a commutator in a DC generator.
I thought commutators are only used in DC motors???

It makes the current generated unidirectional by reversing the output connections each half rotation when the current through the coil should change direction, hence making the output current DC.

[TrueTears]

At the instant when the wire is horizontal, you can approximate it to be a rod falling through a magnetic field... well, at least, one side is falling up and the other is falling down.
Anyway...  I used in the derivation of and it worked out fine.

But that's not a formal proof? When a rod is falling don't you need it to be totally falling down? Not just parts of it?

[kamil9876]

Anyway...  I used Blv in the derivation of emf = \frac{\Delta \Phi}{\Delta t} and it worked out fine.

Can I see?

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soz I edited my post before
I think expression is where is the angle with the horizontal so is the amplitude of the emf graph. Therefore by increasing you are dilating the graph and increasing the emf.

Anyway...  I used Blv in the derivation of emf = \frac{\Delta \Phi}{\Delta t} and it worked out fine.

Can I see?

It's on the previous page

[TrueTears]

What post???

Dw, I'll just remember when you increase the speed is smaller so emf is larger.

[kamil9876]

q4.)

Generators "naturally" produce AC current (if you focus on the actual coil, it will always be AC no matter if you have a split ring, slip ring or fuck all). However we can change this AC into DC by making it such that the ends of the coil switch every half turn. By switching, I mean that the ends of the coil swap with each other the output-wire/terminal thingy that they are touching. SO the switch of connectioncancels out the "natural" change in direction of current. The split ring commutator, just like in DC motors, does this switching.

It makes the current generated unidirectional by reversing the output connections each half rotation when the current through the coil should change direction, hence making the output current DC.

As pointed out by james23

In addition to that, it's a graph so it's always positive, but not constant. But still  apprently qualifies as DC

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Woah duuuuude wait what?

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Which MSN???

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Oh dear would you look at the time

[dcc]

can't sleep.

[dcc]

i'm dropping physics at uni ASAP.  need to do more math.

[TrueTears]

Alright thanks for the helps guys ^^^^

emf = Blv , could you use this formula for a coil in a AC/DC generator (because what 'l' be? the length of the entire "bent" rod or the coils that's wrapped around it?) Or is it just for rods following through a uniform magnetic field?

Thanks!