CFAA Fire Alarm Technician · Question
Three resistors (10, 20, 30 Ohms) are in series with a 120V source. What is the voltage drop across the 20 Ohm resistor?
Total Resistance = 10+20+30 = 60 Ohms. Total Current = 120V / 60 Ohms = 2A. Voltage drop at 20 Ohm = I*R = 2A * 20 Ohms = 40V.
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Question: Three resistors (10, 20, 30 Ohms) are in series with a 120V source. What is the voltage drop across the 20 Ohm resistor?
Answer options:
- 20 V
- 60 V ✅ 40 V
- 120 V
Correct answer: 40 V
Explanation: Total Resistance = 10+20+30 = 60 Ohms. Total Current = 120V / 60 Ohms = 2A. Voltage drop at 20 Ohm = I*R = 2A * 20 Ohms = 40V.
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Question explanations
- The primary power for a fire alarm system must be:
- If a 120VAC primary power circuit for a fire alarm control unit is consuming 60 Watts of power, what is the cu
- In a steady-state DC circuit, if the conductor length is doubled while maintaining voltage and wire gauge, wha
- A resistor is rated at 10 Watts at 24VDC. If the voltage drops to 20VDC, what is the new power dissipation?
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