Convert ohms to milliamperes via Ohm’s law: With a 40 V source and total resistance of 6.8 kΩ, approximately how many milliamperes flow?

Introduction / Context:Reading milliampere-level currents from kilohm-level resistances is a standard task in analog design and instrumentation. This problem emphasizes correct prefix conversion and clean division.

Given Data / Assumptions:

• Voltage V = 40 V.
• Resistance R = 6.8 kΩ = 6800 Ω.
• Compute current I and express it in mA.

Concept / Approach:From Ohm’s law I = V / R. Because R is in kilohms, the result will be in milliamperes; 1 V across 1 kΩ gives 1 mA, a useful mental check known as the 1-k rule of thumb.

Step-by-Step Solution:

Verification / Alternative check:Use the 1-k shortcut: I(mA) ≈ V / R(kΩ) = 40 / 6.8 ≈ 5.88 mA. This quick method matches the detailed computation exactly.

Why Other Options Are Wrong:

• 27.2 mA: Would correspond to about 1.47 kΩ, not 6.8 kΩ.
• 59 mA: Off by a factor of 10; implies R ≈ 0.68 kΩ.
• 590 mA: Two orders of magnitude too large for kilohm resistances at tens of volts.

Common Pitfalls:

• Leaving resistance in kΩ while using volts and forgetting the implied milli result.
• Rounding prematurely and selecting 6 mA vs the more precise 5.9 mA choice.

Final Answer:5.9 mA