Electro magnet-batteries in parallel or series?

Question

Been over 15 years since I have been in school for this stuff and I never used it.
Please refresh my memory:

For an electro-Magnet- what is it that makes it most effective? Wattage, right?
I can’t remember which battery configuration is the (Ohms law reference would be nice)
One for more power- parallel or series?

Parallel is more wattage? Right? I am so ooooooold………

Answer 1

Series will increse Voltage. Parallel provies more AVAILABLE current but this will depend on resistance.
Ok Ohms Law
V= A*R
Wattage is Amps * Volts.
In series, say two D cells you would get 3V. Into the same electromagnet with a given resistance this would in theory double the current over 1.5 Volts of a single battery. It does not always work that way though because the battery has a limit to how much current it can produce.
Now if the resistance is very low you might get more current out of parallel because both batteries are supplying current instead of pressure ( voltage )
Confused yet?
Here's the simplified, sort of. In series you will drive more current through a given resistance as long as you do not exceed what the batery can deliver.

Answer 2

OK, ohms law I = V/R. Know that the resistance of the typical electromagnet is very low, much lower than the internal resistance of the battery. Yes, batteries have resistance too. A "AA" cell has much higher resistance than a car battery. For ohms law, know that it is the TOTAL resistance in the circuit loop that sets the current in a circuit loop.

An electromagnet runs on current. This means you won't be able to put much voltage across it, since the resistance is so low. Since the current will be limited by the resistance inside the battery, then putting batteries in parallel will get you more current, since resistances in parallel divide to give you a lower effective resistance.

Assuming the resistance of the electromagnet is much lower than the resistance of the battery, then:

Two batteries in parallel gives 2X the current.
Three batteries in parallel gives 3X the current, etc.

Beware of batteries getting hot and leaking their internal corrosive fluids, because having a battery's internal resistance limit the current is usually NOT a recommended operating condition for the battery. Usually, I recommend people add in series into the circuit a current limiting device, such as a light-bulb. This should make the project operate much longer, provides an indication the circuit is working, and it keeps the batteries happier.

Answer 3

According to the law
P=V*I where
http://en.wikipedia.org/wiki/Voltage
P = power in watts
V = voltage (potential difference) in Volts and
I = intensity in Amperes

Lets assume we have n batteries connected in parallel which means all the + connected together and all - connected together also, then we have constant Voltage and intensity analog to the number of batteries (Inew=I*n). That means we have more power in watts P=V*Inew=V*I*n.

Now Lets assume we have n batteries in series which means the + pole of each batterie is connected with the - pole of the next.Then we have constant I but Vnew=V*n.That means we have more power P=Vnew*I=V*n*I.

So it seems we have the same power in watts any connection we do. We have more voltage in series connection or more Amperes in parallel connection and that's the difference.

Now as you ask about the electro-magnet power
from the law F=μ^2*I^2*N^2*Α/(2*μ0*L^2)
http://en.wikipedia.org/wiki/Electro-magnet
Where:

F is the force in newtons
B is the magnetic field in teslas
A is the area of the pole faces in square meters
μo is the permeability of free space
N is the number of turns of wire around the electromagnet
I is the current in amperes
L is the length of the magnetic circuit

we have more power as much amperes we have which means we must prefer the parallel connection of the batteries.