When measuring volts, what quantity is being measured?

• A. Electrical current
• B. Electrical resistance
• C. Electrical power
• D. Electrical pressure or force

Answer: (D)

Voltage is the electrical pressure that pushes charges, i.e., the potential difference between two points in a circuit. When you measure volts, you’re determining how much energy per unit charge is available to move charges from one point to another. In practical terms, a voltmeter reads the potential difference across a component or across two points.

This isn’t the same as electrical current, which is the flow of charges (measured in amperes); nor the electrical resistance, which is how strongly a material opposes that flow (measured in ohms); nor electrical power, which is energy per unit time (measured in watts). A helpful analogy is water pressure: voltage is like the pressure difference that pushes water, while current is the flow rate and resistance is akin to the pipe’s friction or width.