Watt Definition: Understanding Power Units

The Watt (symbol: W) is the standard international (SI) unit for measuring power.

Power Calculation Basics

Power is fundamentally defined as the rate at which energy is transferred or work is done per unit of time. The relationship can be expressed mathematically as:

$ \text{Power} = \frac{\text{Energy}}{\text{Time}} $

Watt Equivalence

Using the standard SI units:

• Energy is measured in Joules (J).
• Time is measured in seconds (s).
• Power is measured in Watts (W).

Therefore, the definition of one Watt is derived from these base units:

$ 1 \text{ W} = 1 \frac{\text{J}}{\text{s}} $

This signifies that one Watt of power corresponds to the transfer or conversion of one Joule of energy every second.

Analysis of Options

• 1 erg/sec: An erg is a unit of energy in the CGS system ($1 \text{ erg} = 10^{-7} \text{ J}$). Thus, 1 erg/sec is $10^{-7}$ W, not 1 W.
• 1 Pascal/sec: Pascal (Pa) is the SI unit of pressure. Pascal/sec is not a unit of power.
• 1 m/s: Meters per second (m/s) is the SI unit of velocity. It does not represent power.
• 1 Joule/sec: This directly corresponds to the definition of the Watt based on SI units of energy and time.

Consequently, the correct definition for one Watt is 1 Joule/sec.