1.3 Ohm’s law and power
Outcome 3 of 9 in domain 1 · Foundations, direct current
Calculate, predict heating.
My targets
I declare:
Exercises
By target, three levels: the bare notion, the application, the reasoning. Calculations, true-or-false and choices are checked here; for an essay, you read the answer and judge yourself.
Target 10 of 9
Calculate the third quantity from two (V, I, R) without a table.
Target 20 of 9
Predict the dissipated power and choose a resistor of sufficient rating, with a working margin.
Target 30 of 9
Measure V and I on a real circuit and recover R within 5 %.
Target 40 of 9
Explain why a wire that’s too thin heats up, with the calculation, and choose a wire gauge for a given current.
Target 50 of 9
Read a wire gauge table (AWG) and calculate the voltage drop over ten metres of cable for a given current.
Target 60 of 7
Diagnosis: a burnt resistor on a board, say why from the schematic, and what it protected.
Read
Kuphaldt, Lessons in Electric Circuits, volume I (DC), chapter 2: Ohm’s Law. "How voltage, current, and resistance relate", "Calculating electric power" and "Resistors" are the whole outcome; "Nonlinear conduction" is the door to the diodes of domain 3. Wire is in chapter 12, Physics of conductors and insulators: "Specific resistance" gives resistance per length and does the gauge calculation by drop, "Conductor ampacity" the one by heat.