My son has been tasked with constructing a wheatstone bridge. I think he understands the basic physics and the math behind it, but he has never built ANY sort of electronics previously. We have several questions:

1. can he just assemble this on a breadboard? (it's not a long-term exhibit, just to demonstrate the properties)

2. his teacher wants him to actually 'make' resistors - no idea how to do this, and he's not finding anything online...especially as three of these need to be of known and identical resistance (don't they??) - can these just be made out of copper wire? metal plates?

3. in a real, working WB, one of the resistors needs to be variable, right?? I assume he's not going to have to recreate a 'decade box', but if so, any thoughts on how to go about this?

Any sources or tips on getting started would be most welcome. He is really struggling to figure all of this out quickly. Thanks!

 

A breadboard is over the top. An old shoebox would be a better housing.

I expect your lad has done 'slide wire potentiometers in physics' first. you can make resistors in this way from resistance wire or old electric fire bars.

However I expect what the teacher wants is for the lad to make up non standard resistors to switch into circuit by combining standard ones. He will also need to select for matching if making steps.

For advice on making resistors look at post 1 of this thread

http://forum.allaboutcircuits.com/showthread.php?t=12878&highlight=tips+tricks&page=3

For construction ideas look at this link:

http://physics.kenyon.edu/EarlyApparatus/Electrical_Measurements/Potentiometer/Potentiometer.html

 

Check these chapters of the AAC book out...

http://www.allaboutcircuits.com/vol_1/chpt_8/12.html

http://www.allaboutcircuits.com/vol_6/chpt_3/6.html

http://www.allaboutcircuits.com/vol_6/chpt_3/14.html

Lots of science fair material in the experiments volume (VI).