Correct option is C
For measuring the power in single-phase systems, different methods are typically employed based on the phase system in question.
Here's an analysis of the options provided:
(a) Polyphase wattmeter:
This term is generally used to describe a wattmeter capable of measuring power in systems with more than one phase, such as three-phase systems.
It is not specific to single-phase measurements.
(b) Three wattmeter method:
This method is specifically used for three-phase power measurement where three wattmeters are used to measure the power in each of the three phases.
This is not suitable for single-phase systems.
(c) One wattmeter method:
This method involves using a single wattmeter to measure the power in a single-phase system.
It's the most straightforward approach for measuring power in such systems, involving only the measurements of voltage and current, and the phase angle between them if necessary.
This method is directly suited for single-phase applications and is commonly used due to its simplicity and effectiveness in such setups.
(d) Two wattmeter method:
This method is used primarily in three-phase systems to measure total power by using two wattmeters.
It’s not applicable for single-phase measurements.
Given these descriptions, the correct answer for a method used exclusively to measure the power of a single-phase system is (c) One wattmeter method.
