can I use two 103 caps in a row if I havent any more 104s?

This is prolly a real Noooooby dumb question but, I need a 0.1uF capacitor but havent any left. But I have heaps of others. Can I do something like the attached, or do I have to go to radioshack and pay 2 bucks just for 2 new 0.1uf’s?

Screen shot 2011-04-14 at 2.14.31 PM.png

Your drawing shows them in series. To build a 0.1 from 10 off 0.01 you need to arrange them in parallel

oh, ok. like this then?

Screen shot 2011-04-14 at 3.18.03 PM.png

Yes but what do you want them for? Sometimes distributing that many capacitors adds to the inductance and they are not as good at certain things.

as pulldowns for a 3 axis accelerometer.....

If they are for decoupling the exact value is usually not very important compared to the fact that there is decoupling. The more current you switch and the faster you switch it the more decoupling.

If the 10nF caps you have aren't ceramic, they aren't going to be great for decoupling BTW.

as pulldowns for a

Capacitors are not used for pull down only resistors.

Otherwise MarkT is right, inductance in a decoupling cap increases the self resonance frequency and makes them less effective. Smoothing on the other hand is not so affected.

or do I have to go to radioshack and pay 2 bucks just for 2 new 0.1uf's

Someone is having a laugh you should not need to spend more than $0.1 on a capacitor and many times it will be cheaper.

Anyway two 10nF capacitors in parallel will only give you 20nF if you need 100nF then you need 10 caps not two like you say in the post subject.