Tech A says that when checking a voltage drop across an open switch, a measurement of 12 volts is normal. Tech B says that when checking voltage drop across an open switch, a measurement of 12 volts means there are 12 volts on each side of the switch. Who is correct

Tech B is correct.

Explanation:

The voltage drop between the two terminals of a circuit is the measurement of the potential difference between the two terminals.

If and ( assuming ) are potentials at terminal 1 and terminal 2 of the given open circuit.

According to A, the measurement of the potential drop is 12 volts, i.e

The measurement of potential difference

= 12 volts which is correct.

But according to B, a measurement of 12 volts means there are 12 volts on each side of the switch ( volts and volts), i.e

According to the claim of B, the potential difference (or drop) across the terminals is

but the measured potential drop is 12 volts, so B is wrong.

Hence, Tech B is correct.

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )