[TwoHandedSword]

It's been a while since I've had a follower, or played a techie. But IIRC, you place the items in Magnus's inventory, then call up the "What can you build for me?" dialogue.

Then, when the tech screen comes up, click through the various colleges until you find the one that contains what you're trying to have him build. Magnus's build scheme is in the areas of Smithy and Mechanical; that means with the right materials, he can make Pure Ore and Spike Traps, but not Electric Light or Strong Poison.

So you either have to take the required ranks yourself, or seek out another follower who can build from the Electrical schematic.

*SPOILER BELOW*

That would be Sebastian, in the slum section of Tarant southwest of the bridge, known as the Boil. And I believe you have to be neutral, evil, or a Persuasion master to recruit him. You definitely have to be a fairly high level, as the Boil is not a very nice place.

FWIW, one of the most useful tech items in the game is in the Electrical college: the Charged Ring, which gives a +2 DX bonus per ring when worn!

*END SPOILER*