What is the equivalent resistance of six 120-ohm resistors connected in parallel?

• A. 12Ω
• B. 20Ω
• C. 60Ω
• D. 720Ω

Answer: (B)

To determine the equivalent resistance of resistors in parallel, you use the formula for parallel resistance. For n resistors, the formula is:

1/Req = 1/R1 + 1/R2 + 1/R3 + ... + 1/Rn.

In this case, with six resistors, each having a resistance of 120 ohms, the equation becomes:

1/Req = 1/120 + 1/120 + 1/120 + 1/120 + 1/120 + 1/120.

This simplifies to:

1/Req = 6/120, which leads to:

1/Req = 1/20.

To find Req, you take the reciprocal of both sides:

Req = 20 ohms.

This shows that the equivalent resistance for six 120-ohm resistors connected in parallel is 20 ohms. This result illustrates how adding more resistors in parallel decreases the total resistance, which is a fundamental principle of parallel circuits in electronics.