Red Seal Electrician Practice
DC circuitsQuestion 635 of 1506

A student has a 12 V supply with a 2 kΩ and a 4 kΩ resistor in series. The student finds the current as 12 V / 4 kΩ = 3 mA. What is wrong with this?

  1. The total voltage was used with one resistor, not the same two points.
  2. The 4 kΩ value must be divided by 1000 first in every case.
  3. The current in a series circuit must be found from the 2 kΩ resistor.
  4. The supply voltage must be doubled for any series circuit.
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Correct answer: The total voltage was used with one resistor, not the same two points.

Use the total resistance, 6 kΩ, with the total voltage: I = 12 V / 6 kΩ = 2 mA.

Source: Lessons in Electric Circuits I: DC (Kuphaldt), 5.2: Simple Series Circuits

Practice dc circuits

Questions last reviewed: 18 October 2026