The New Hotness

Some ex post facto notes from the first SquidWrench Electronics Workshop, in the expectation we’ll run the series from the start in a while. I should have taken pictures of my scribbles on the whiteboard.

Define:

• Voltage – symbol E (Electromotive Force or some French phrase), unit V = volt
• Current – symbol I (French “intensity” or some such), unit A = ampere
• Resistance – symbol R (“resistance”), unit Ω (capital Greek Omega) = ohm

Introduce Ohm’s Law & permutations, postpone calculations.

Measure the actual voltage of assorted cells & batteries. Identify chemistry, internal wiring:

• 1.2 = nickel-cadmium or nickel-metal-hydride
• 1.5 = carbon-zinc or alkaline
• 2 V = lead-acid
• 3.0 = primary lithium
• 3.6 – 3.7 = rechargeable lithium, several variations
• 4.8 = 4 x 1.2 V
• 7.2 = 6 x 1.2 V
• 7.4 = 2 x 3.6 V
• 9.6 = 8 x 1.2 V
• 10.8 = 3 x 3.6 V
• 12 = 6 x 2 V

Measure various resistors, favoring hulking finger-friendly sandstone blocks.

Introduce metric prefixes:

• Engineering notation uses only multiple-of-three exponents
• μ = micro = 10^-6
• m = milli = 10^-3
• k = kilo = 10³
• M = mega = 10⁶

Discuss resistor power dissipation vs. size vs. location, postpone power formula.

Clip-lead various resistors to various batteries, measure voltage & current.

Introduce fixed & variable power supplies, repeat resistor measurements.

Now compute permutations of Ohm’s Law using actual data!