# True or False

The magnitude of the current depends on the rate at which the magnet is moving in and out of the solenoid.

True or false

HallsofIvy
Homework Helper
Have you considered flipping a coin?

Now you know you are expected to make some effort yourself. In this case, I assume you are talking about a generator consisting of a magnet moving inside a coil- You should have said that. What does your text book say about generators? What formulas do you know for current?

since voltage induced is proportional to the rate of change of B-field,i think magnitude is also dependent on it?

i really have no clue, im a noob

Hootenanny
Staff Emeritus
Gold Member
i really have no clue, im a noob
Consider Faraday's Law together with Ohm's law.

man, i have too hand this in tomorrow and im at risk of failing can you cut a guy a break

Hootenanny
Staff Emeritus
Gold Member
man, i have too hand this in tomorrow and im at risk of failing can you cut a guy a break

I will help you, but I am not going to give you the answer. However, if you do put some effort in, you will have the answer within minutes. Now, what is Faraday's law?

Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil.

Hootenanny
Staff Emeritus
Gold Member
Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil.
Correct, this can be represented mathematically;

$$V=\frac{\Delta\Phi}{\Delta t}=\frac{\Delta (BA)}{\Delta t}$$

Next, what is ohm's law?

Ohm's law states that, in an electrical circuit, the current passing through a conductor is directly proportional to the potential difference applied across them provided all physical conditions are kept constant.

Hootenanny
Staff Emeritus
Gold Member
Ohm's law states that, in an electrical circuit, the current passing through a conductor is directly proportional to the potential difference applied across them provided all physical conditions are kept constant.
And mathematically;

$$I = \frac{V}{R}$$

So, can you now combine the two equations?

As an aside, I do hope that you are taking the time to understand these laws and are simply not copying and pasting them directly from the internet.

how do you comine them

Hootenanny
Staff Emeritus
Gold Member
Substitute Faraday's law for the V in ohm's law.

cant you help a guy out

Hootenanny im studying for a test right now thats in an hour i really dont have time.

Hootenanny
Staff Emeritus
Gold Member
I will do the substitution for you, however, you must draw your own conclusions. So now we can say that;

$$I = \frac{\frac{\Delta (BA)}{\Delta t}}{R} = \frac{\Delta (BA)}{R\cdot\Delta t}$$

Now, if you change that rate at which you move the magnet through the coil, do any terms change in the above equation?

yes they do

Hootenanny
Staff Emeritus
Gold Member
yes they do
So does the current change?

yes

so my initial question is False

or.........

Hootenanny
Staff Emeritus
Gold Member
The magnitude of the current depends on the rate at which the magnet is moving in and out of the solenoid.
If the current does change when you change the rate at which the magnet moves then the above statement is ____

true.........

Hootenanny
Staff Emeritus
Gold Member
true.........

Sounds good to me

Hootenanny does the magnitude of the current depend on the strength of the magnet.

P.S because weave formed such a close friendship over these past hours do you think you might be able to answer my other question.... pleaseeeeee

is this for real? you are studying for a test and can't combine 2 equations? is this grade 11 or something?

yeah.............