Calculating Resistance from Voltage and Current

Step 1

Gather the data provided in the problem: the voltage (V) and the current (I).

Step 2

Standardise the units. If the voltage is expressed in kilovolts (kV) or the current in milliamperes (mA), convert them to volts (V) and amperes (A) respectively. Accurate unit conversion is essential for a correct calculation.

Step 3

Apply Ohm’s Law, R = V ÷ I. For example, a 120‑V circuit that delivers 10 A of current has a resistance of 12 Ω.

Calculating Resistance from Power and Current

Step 1

Identify the power (P) and the current (I) values supplied by the problem.

Step 2

Convert the power to watts (W) and the current to amperes (A). Avoid using kilowatts or kilowatt‑hours unless you perform the necessary conversion.

Step 3

Square the current: I². For a 10 A current, I² = 100 A².

Step 4

Use the formula R = P ÷ I². For a 120‑W load with I² = 100 A², the resistance is 1.2 Ω.

References

• “College Physics” by Raymond Serway and Jerry Faughn, 2000.