Hi,

I want to try wrapping cables around a steel bar and connecting 9V battery to it in order to experiment with electro-magnets. Should I be connecting some resistance to cable or does making an electro-magnet act like a resistance in the circuit?

 

A 9V battery cannot provide a lot of current.

 

Do you mean I won't see the effects of magnetism even without using any resistor? How many amps do I need in order to observe the effects of electromagnetism? I have a feeling that 220V AC 50Hz would be too much of a current to play with.

 

You are basically short circuiting the wire its going to get very hot.You can use 4x1.5V AA batteries to play with small electromagnets.

 

A 9V battery cannot provide a lot of current.

I think you can get many amps for a short time (seconds?) via a dead short across a new 9V Alkaline. It won't last long, though, and it will get hot.

 

Hi,

I want to try wrapping cables around a steel bar and connecting 9V battery to it in order to experiment with electro-magnets. Should I be connecting some resistance to cable or does making an electro-magnet act like a resistance in the circuit?

Get yourself some fine magnet wire and run *lots* of turns. You can compute the DC current by measuring the DCR of the coil, and dividing that into the battery voltage. The higher the coil resistance, the longer your battery will last.

 

I have actually put a multimeter on the 10A scale across a new 9V and it only gave about 1.5A.

Edit:

Magnetic field = Current x turns.

To get a good magnetic field from a 9V, put many many turns. Enough to create a resistance of about 18 Ohms, and it will draw 500mA, and be dead in less than 1 hour.

Bob

 

I just got 2.3A off a new Duracell.

 

If you want you could buy 12V/3A transformer since those are pretty cheap and then make a simple power supply using rectifier bridge and a capacitor.
You cant use voltage regulators since they have short circuit protection and will over heat and die.

 

I made a coil that created a resistance of 1 ohm and it drew 750mA current, but I didn't see any magnetism. I will try later with better equipment.

I guess my battery is about to be depleted

 

Wire needs to be isolated it cannot be bare.

 

Hi,

I want to try wrapping cables around a steel bar and connecting 9V battery to it in order to experiment with electro-magnets. Should I be connecting some resistance to cable or does making an electro-magnet act like a resistance in the circuit?

The only thing a resistor will do is waste some of the power as heat.

If you're using a PP3 type 9V battery - they're amongst the lowest energy density batteries you can get.

Do a search for; "ampere-turns" - every turn of winding you put on has its magnetic field around it and contributes to the whole.

 

Tell us about your coil, what kind of wire, how many turns, and what the core is made of.

Bob

 

Try using an automotive battery, more current available.
Max.

 

soft iron works best for that. hardened steel has different characteristics. I agree, more turns of fine wire, like #26 or so. a heavy cable will have way too little resistance to limit the current, and if you use a resistor, the current will be too low for the ampere turns.