What is the purpose of a wattmeter?

The purpose of a wattmeter is to measure electrical power in watts, making it a vital instrument in the analysis and monitoring of electrical systems. It achieves this by measuring both the voltage across and the current flowing through a circuit, allowing it to calculate the power being consumed or generated in real-time. This capability is essential in various scenarios, such as in electrical installations, where understanding power usage can aid in optimizing energy efficiency and ensuring that equipment operates within safe limits.

In contrast, measuring voltage is not its primary function, which is why that option does not capture the essence of what a wattmeter does. Testing circuit insulation falls outside its purpose, as that would typically involve insulation resistance testers instead. Surge protection devices serve to protect electrical systems from transient voltages, which is distinct from the wattmeter's function of measuring power consumption. Thus, the wattmeter's specific role in measuring electrical power sets it apart from other electrical instruments.