1 Joule per second (1 J/s)
Explanation
Power is defined as the time rate at which work is done or energy is transferred. In the International System of Units (SI), the standard unit of power is the Watt (W), named after the Scottish engineer James Watt.
Option Analysis:
- 1 Joule per second (1 J/s) is Correct: Mathematically, Power ($P$) is calculated as Work ($W$) divided by Time ($t$). Since the SI unit of Work is the Joule (J) and the SI unit of Time is the Second (s), one Watt is defined as one Joule of energy transferred or work done per second ($1 \text{ W} = 1 \text{ J/s}$).
- 1 Newton per second (1 N/s) is Incorrect: 1 Newton per second ($1 \text{ N/s}$) represents the rate of change of force, which is not a standard physical quantity for power.
- 1 Kilogram metre per second is Incorrect: 1 Kilogram metre per second ($1 \text{ kg m/s}$) is the SI unit of Momentum ($p = \text{mass} \times \text{velocity}$).
- 1 Joule second (1 J-s) is Incorrect: 1 Joule second ($1 \text{ J}\cdot\text{s}$) is the unit of Action or Angular Momentum (dimensionally equivalent to Planck's constant).
Key Takeaway:
The Watt is a derived SI unit representing the rate of energy consumption or work done, defined strictly as $1 \text{ Joule per second}$.