Three resistors are wired in parallel. Two have a value of 12 ohms, one of 6 ohms. What is the total resistance?

Three resistors are wired in parallel. Two have a value of 12 ohms, one of 6 ohms. What is the total resistance?

• A. 6
• B. 12
• C. 3
• D. 4

Answer: (C)

When resistors are in parallel, you sum their conductances (the reciprocals of the resistances) to find the total. So add 1/12 + 1/12 + 1/6. The two 12-ohm resistors give 1/12 + 1/12 = 1/6, and 1/6 plus another 1/6 equals 1/3. The reciprocal of 1/3 is 3, so the total resistance is 3 ohms. A quick check: two 12-ohm resistors in parallel give 6 ohms, and 6 ohms in parallel with 6 ohms also gives 3 ohms.

When resistors are in parallel, you sum their conductances (the reciprocals of the resistances) to find the total. So add 1/12 + 1/12 + 1/6. The two 12-ohm resistors give 1/12 + 1/12 = 1/6, and 1/6 plus another 1/6 equals 1/3. The reciprocal of 1/3 is 3, so the total resistance is 3 ohms. A quick check: two 12-ohm resistors in parallel give 6 ohms, and 6 ohms in parallel with 6 ohms also gives 3 ohms.