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.

correct it is c.) b b

see earlier