Which statement correctly describes the ohm?

• A. It is the unit of resistance.
• B. It is the unit of current.
• C. It is the unit of voltage.
• D. It is the unit of power.

Answer: (A)

Resistance is the opposition to the flow of electric current, and the ohm is the unit used to express that opposition. One ohm equals one volt per ampere, which fits neatly with Ohm’s law V = I × R. This means a component with 1 ohm of resistance will have 1 V across it when 1 A flows, illustrating what resistance measures. That’s why the statement that the ohm is the unit of resistance is correct. Other quantities use different units—current is measured in amperes, voltage in volts, and power in watts—so they aren’t described by the ohm.