What is the equivalent resistance of three 15 ohms resistors in parallel [MCQ]

Statement: Three resistors of 15 ohms are connected in parallel. The equivalent resistance is:

1. 12.5 ohms
2. 10 ohms
3. 5 ohms
4. 3 ohms

Answer: 5 ohms

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Discussion:

Brief solution:

The basic formula for parallel resistors is:

In case of three resistors:

1/R(eq) = 1/R(1) + 1/R(2) + 1/R(3)

Solving this we obtain R(eq) = 5 ohms

Point to Remember

Whenever ‘n’ number of resistors all having same resistance (Lets say ‘x’) are connected in parallel, the equivalent resistance equals x divided by n.

That is R(eq) = x/n

In our case:

R(eq) = 15/3 = 5 ohms which is the equivalent resistance.

Further Reading:

1. Resistors Book [Download]
2. Basic Electrical Formulas
3. MCQs on Basic Electrical Quantities