High-voltage DC application: determine the current when 18 kV is applied across a 15 kΩ resistance (state the result in appropriate SI units).

Introduction / Context:
Ohm’s law scales easily to kilovolt and kilo-ohm ranges common in high-voltage testing and insulation checks. Accurate unit handling (kV, kΩ) prevents order-of-magnitude mistakes and ensures safe design margins.

Given Data / Assumptions:

• Voltage V = 18 kV = 18,000 V.
• Resistance R = 15 kΩ = 15,000 Ω.
• Use I = V / R for a purely resistive element.

Concept / Approach:

Convert both quantities to base SI units (volts, ohms), then compute current. Alternatively, use ratio of prefixes directly: kV/kΩ cancels the kilo factor, leaving amperes.

Step-by-Step Solution:

Verification / Alternative check:

Prefix method: 18 kV / 15 kΩ = (18/15) kV/kΩ = 1.2 A because k cancels. Consistent with the calculation above.

Why Other Options Are Wrong:

12 A is 10× too large; 120 mA is 10× too small; 12 mA is 100× too small.

Common Pitfalls:

Failing to convert kV and kΩ consistently; treating kilo as 1024 instead of 1000 in SI electrical units.

Final Answer:

1.2 A