How Much Current Should Flow Through My Electromagnet Experiment?

[lekh2003]

Homework Statement

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I am working on a lab report regarding the creation of an electromagnet using an iron core solenoid (just a nail wrapped with copper insulated wire). Before continuing with the creation of the electromagnet, I had to answer some questions regarding my knowledge of electromagnets.

One of those questions is asking how much current would be flowing through the electromagnet.

I know that the voltage is 3 volts, I am probably going to use about 0.5 meters of enameled 24 AWG copper wire.

Homework Equations

V = IR

R = ρL/A

The Attempt at a Solution

My attempt at this problem was simple. I thought that the only resistance would be the copper wire. To find the current, I used the equation:

I = (VA)/(ρL)

The problem I really had was that my value for current was close 300 A. I was worried to continue with the experiment knowing that 300 A are going through the wire. Am I missing something here? Is there some resistance I am not taking into account? Should I be using more wire?

I think the solution is to use much much more wire to create more resistance (maybe 5 m?), I just wanted to check if I'm right.

 

[cnh1995]

Is there some resistance I am not taking into account?

What power source are you using? Dry cells?
You should consider the internal resistance of the cell. It would be more than the copper resistance.

 

[lekh2003]

What power source are you using? Dry cells?
You should consider the internal resistance of the cell. It would be more than the copper resistance.

I'm using two D batteries in a generic D battery holder. How much internal resistance would a D battery have? (The battery is unused)

 

[cnh1995]

I'm using two D batteries in a generic D battery holder. How much internal resistance would a D battery have?

You can look this stuff up.
https://www.google.co.in/url?sa=t&s...jChwQFggwMAI&usg=AOvVaw3ckhXx3rxGd0keod3u5NEA

 

[cnh1995]

I was worried to continue with the experiment knowing that 300 A are going through the wire. Am I missing something here? Is there some resistance I am not taking into account? Should I be using more wire?

You won't be able to keep the current flowing for long if it is a few amperes (forget 300A). The battery will quickly discharge. I believe these batteries are supposed to be used with electronic circuitry, where the current is of the order of a few mA.

 

[lekh2003]

You won't be able to keep the current flowing for long if it is a few amperes (forget 300A). The battery will quickly discharge. I believe these batteries are supposed to be used with electronic circuitry, where the current is of the order of a few mA.

I get it now, I can reason that the initial current calculation is not a representation of the entire experiment. I have done my calculations accounting for internal resistance and have gotten 14 A, which I can expect to decrease with time to an order of mA.

Thanks