Voltage across a resistor — apply Ohm’s law with unit prefixes: What is the voltage across a 2.2 kΩ resistor if 3 mA of current flows through it?

Difficulty: Easy

6.6 V
7.33 V
1.4 V
0.8 V

Correct Answer: 6.6 V

Explanation:

Introduction / Context:
This is a direct substitution problem using Ohm’s law. Correct handling of kilo-ohms and milliamperes is critical to avoid order-of-magnitude errors in the final voltage.

Given Data / Assumptions:

R = 2.2 kΩ = 2200 Ω.
I = 3 mA = 0.003 A.
Linear resistor, steady state.

Concept / Approach:
Use V = I * R, ensuring that units are in base SI prior to multiplication. Then express the answer in volts with sensible significant figures reflecting the inputs.

Step-by-Step Solution:

Convert: R = 2200 Ω, I = 0.003 A.Compute V = I * R = 0.003 * 2200.Multiply: 0.003 * 2200 = 6.6 V.Answer: 6.6 V across the resistor.

Verification / Alternative check:
Back-check current: I = V / R = 6.6 / 2200 ≈ 0.003 A = 3 mA, confirming the result.

Why Other Options Are Wrong:

7.33 V: not supported by 2.2 kΩ at 3 mA.1.4 V and 0.8 V: too small by factors of about 4.7 and 8.25 respectively.

Common Pitfalls:
Leaving R in kΩ and I in mA without adjusting; misplacing decimal points when using prefixes.

Voltage across a resistor — apply Ohm’s law with unit prefixes: What is the voltage across a 2.2 kΩ resistor if 3 mA of current flows through it?

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