CSLB C-10 Electrical ContractorElectrical Theory and CalculationsEasy
A series circuit consists of three resistors: R1 = 5 ohms, R2 = 10 ohms, and R3 = 15 ohms. If the circuit is connected to a 60V DC source, what is the approximate total current flowing through the circuit?
- A6 A
- B4 A
- C3 A
- D2 A
Show answer & explanationAnswer & explanation
Correct answer: D. 2 A
First, calculate the total resistance (Rt) of the series circuit: Rt = R1 + R2 + R3 = 5Ω + 10Ω + 15Ω = 30Ω. Then, use Ohm's Law to find the total current (I): I = V / Rt = 60V / 30Ω = 2A.
Why the other options are wrong
- A. This would be if the total resistance was 10 ohms, which is incorrect.
- B. This could be a miscalculation or incorrect application of Ohm's Law.
- C. This might result from a calculation error for total resistance or current.
Series Circuit Current
The total current in a series circuit is the same through all components and is calculated by dividing the total voltage by the total equivalent resistance.
- Rt = R1 + R2 + R3 + ...
- I_total = V_total / R_total
- Current is constant throughout the series circuit.
Memory trick: Series: Sum Resistance First, then Ohm's Law for Current.