A series circuit has three resistors of 4 ohms each. The voltage drop across each resistor is 4 volts. Technician A says that the source voltage is 12 volts. Technician B says that the total resistance is 18 ohms. Which technician is correct?

Technician A

Explanation:

In the series connection the total resistance is equal to the sum of the individual resistance of the resistors.

Therefore,

For the given case total resistance will be, R = 4 + 4 + 4 = 12 Ω

Hence,

Technician B is wrong.

Also,

Total voltage in series circuit is given as

V = V₁ + V₂ + V₃ [i. e sum of the voltage across respective resistors]

or

V = 4 + 4 + 4 = 12V

Hence,

Technician A is correct.