Using Ohm's law, what electromotive force (voltage) is required to drive a current of 20 A through a 500 Ω resistor (assume steady DC conditions)?

Introduction:
This is a direct application of Ohm's law to determine the voltage required for a specified current through a known resistance. Such calculations are common in sizing power supplies and checking feasibility in high-resistance or high-current paths.

Given Data / Assumptions:

• Current I = 20 A (DC).
• Resistance R = 500 Ω.
• Ideal source and resistor; temperature effects neglected.

Concept / Approach:
Ohm's law states V = I * R. With the current and resistance provided, compute the voltage directly. The magnitude here will be large because both I and R are sizable, highlighting the power implications in practical designs.

Step-by-Step Solution:
1) Write the formula: V = I * R.2) Substitute values: V = 20 A * 500 Ω.3) Multiply: V = 10,000 V.4) State the result clearly with units: 10,000 volts (10 kV).

Verification / Alternative check:
Power check: P = V * I = 10,000 * 20 = 200,000 W (200 kW). This confirms that such a condition implies enormous power dissipation in the resistor and is impractical without special hardware, reinforcing that the arithmetic is consistent.

Why Other Options Are Wrong:
0.04 V, 2.5 V, 25.0 V, 100 V: All are orders of magnitude smaller than required by V = I * R for 20 A through 500 Ω.

Common Pitfalls:
Mixing units (kΩ vs Ω or mA vs A) and forgetting that large currents through large resistances require very high voltages. Always use base SI units when in doubt.

Final Answer:
10,000 V