does anyone on here know anything about electronic circuits? i just need answers to a couple of questions about a simple battery & motor circuit.

Cheers!

Well i did A-Level physics but it depends how simple everything is as to whether I'll be any help

well, i have a pre-existing circuit, which is:

1 - 7.2volt (DC) 1.3amp battery
2 - an electric motor
3 - a trigger switch

this was bought as a set, and all works fine together. i need to add into this; a mini fan, the sort used for cooling CPU's or graphics cards.

Can i just stick in any fan i can get, or does it have to 'match' things in the circuit i already have? ie if the voltage on the battery is too high for it, would it just melt/not work?

ive had a look round, and i can get a 7volt rated fan. does this mean it needs 7 volts to run it? bearing in mind the existing motor will be attached as well? would i need a 14 volt battery to run a 7volt rated fan & a 7volt motor? provided they where both running at the same time? or is that not how electricity works?

i don't really know anything about electronics, or how this volts/amps business works.

any suggestions?

I think it will be alright... how are they linked up? In series or in parrallel?

The 7volt motor means it needs that power rating to run, and that implied current to supply that voltage. So basically 7volts maybe enough, but it depends on the resistance of the other components and the architecture of your circuit. A 14volt battery will have a higher current (amps), so you might need a resistor in there to step down the current.

You can actually work out how much voltage is going to be passing through each component. It depends what layout your putting them in series or parrallel. On a parrallel it splits the current equally, in series its an addition I think.

Damn hang on, my little brother does electronics... i'll ask him.

erm, basically what I'm meant to say is, if your fan will run on ~0.65amps, then you can put the electric motor and the fan in parrallel, if it needs more than that, you can put your two batteries in series, and then put the motor and fan in parrallel, that will mean each component gets 1.3amps of current, which is 7.2volts.
So to summarise again, that means that if you setup your circuit so you have your 7volt battery, your switch, then put the motor and the fan in parrallel and link back to the battery, that should be fine... if the fan doesn't work, add another 7volt battery and it should ensure both components get 7 volts. That's the rough answer without knowing what the resistance of both your fan and your motor will be, and the layout of the circuit (then you can hammer out the old V=IR )

I think that makes sense, if your house burns down its not my fault.