Question

A circuit contains two devices that are connected in parallel. If the resistance of one of these devices is 12 ohms and the resistance of the other device is 4 ohms, the total resistance of the two devices is
A. 0.333 ohms.
B. 16 ohms.
C. 0.0625 ohms.
D. 3 ohms.

Answer 1

Answer

3 Ohms

Explanation

when the resistors are in series, the resistance in the circuit increases. For example, if two resistors, R1 and R2 are in series, the combined resistance is R1+R2.

When connected in parallel, the total resistance is the reciprocal of (1/R1 + 1/R2)

In this case the resistors are in parallel.

Total resistance = (1/12 + 1/4)⁻¹

= (1/3)⁻¹

= 3 Ohms

Answer 2

The formula for calculating total resistance is 1/Rt = 1/R1 + 1/R2. Inputting the values given in the question, this formula becomes: 1/Rt = 1/12 + 1/4, which is 0.3 recurring. Therefore the answer is A, 0.333 Ohms.