Deep Dive: T5D06
The correct answer is A: 3 ohms. For a circuit that draws 4 amperes from a 12-volt source, the resistance is 3 ohms. Using Ohm's Law: R = E / I = 12 / 4 = 3 ohms. This is a direct application of Ohm's Law. When a circuit draws 4 amperes from a 12-volt source, the resistance must be 3 ohms. This calculation is fundamental for understanding how circuits work and for selecting proper components. The formula shows that lower resistance allows more current to flow for a given voltage, which is important for circuit design and troubleshooting.
Why Other Answers Are Wrong
Option B: Incorrect. 16 ohms would be close to adding voltage and current (12 + 4), but resistance is voltage divided by current, not added. Option C: Incorrect. 48 ohms would be multiplying voltage and current (12 × 4), which gives power (48 watts), not resistance. Option D: Incorrect. 8 ohms would be dividing voltage by half the current, which doesn't match the given values.
Exam Tip
Resistance = Voltage / Current. Remember: R = 12V / 4A = 3 ohms. Simple division gives the answer.
Memory Aid
**R** = **1**2V / **4**A = **3**Ω (think '12/4 = 3')
Real-World Example
You're checking your transceiver's power consumption. It draws 4 amperes from a 12-volt battery. Using R = E / I, you calculate the effective resistance: R = 12 / 4 = 3 ohms. This helps you understand the load and verify the power supply can handle it.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T5D
Reference: 2022-2026 Question Pool · T5 - Electrical principles
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T5D topic.