According to the International System of Units (SI), what is the derived unit used to measure power, that is, the rate of doing work or transferring energy per unit time?

Introduction / Context:
This question focuses on the SI unit of power. Power tells us how quickly work is done or energy is transferred. For example, two machines may do the same amount of work, but the one that does it in less time has higher power. Correctly identifying the SI unit of power is essential in mechanics, electricity and many engineering applications.

Given Data / Assumptions:

• Power is defined as work done or energy transferred per unit time.
• The options include Boyle, watt, newton and pascal.
• We are working within the SI system of units.
• No calculation is required; only recognition of the correct unit is needed.

Concept / Approach:
In SI, power P is defined as P = W / t, where W is work or energy in joules and t is time in seconds. The derived unit of power is the watt (symbol W), named after James Watt. One watt equals one joule per second. Newton is the unit of force, pascal is the unit of pressure and Boyle is not a unit at all but the name of a scientist associated with gas laws. Therefore, watt is the correct SI unit of power.

Step-by-Step Solution:
Step 1: Recall that work done W is measured in joules and time t in seconds. Step 2: Power P is defined as P = W / t, which has units of joule per second. Step 3: Recognise that the SI derived unit corresponding to joule per second is called watt (W). Step 4: Note that newton (N) is the SI unit of force and appears in F = m * a, not in the definition of power. Step 5: Understand that pascal (Pa) is the SI unit of pressure, defined as newton per square metre. Step 6: Identify that Boyle refers to Robert Boyle, a scientist known for Boyle law, and is not the name of a unit. Step 7: Conclude that the only correct SI unit of power among the options is watt.

Verification / Alternative check:
To verify, think about the label on electric appliances such as bulbs, fans or heaters. They are typically rated in watts or kilowatts, for example 60 W, 100 W or 1 kW. These ratings tell you how much electrical power the devices consume. In power plant ratings, you often see megawatt or gigawatt. None of these use newton or pascal as power units, confirming that watt is the standard SI unit for power.

Why Other Options Are Wrong:
Boyle is the name of a scientist and has no official role as a unit in the SI system. Newton is the SI unit of force and is used in mechanics to measure how strongly one body pushes or pulls another. Pascal is the SI unit of pressure, measuring force per unit area, not the rate of doing work.

Common Pitfalls:
Students sometimes confuse related physical quantities because the same scientist names appear in multiple contexts, such as Boyle law and Newton laws. Another mistake is to think that any familiar scientific name could be a unit. To avoid this, memorise the core SI units and their meanings: watt for power, newton for force and pascal for pressure. This simple mapping will help you answer unit based questions quickly and accurately.

Final Answer:
The SI derived unit used to measure power is the Watt (W), equal to one joule per second.