What type of component is a combining device made of an ammeter and a voltmeter?

A combining device made of an ammeter and a voltmeter is classified as a wattmeter because it is specifically designed to measure electrical power in an electrical circuit. A wattmeter combines the measurements from both the ammeter, which measures the current, and the voltmeter, which measures the voltage. By multiplying these two values together (taking into account the phase difference in AC systems), the wattmeter can effectively calculate the power being consumed or produced in watts.

The other options refer to different types of measurement tools: a multimeter can also measure voltage and current but is not exclusively designed for power measurement; an oscilloscope is used for visualizing waveforms of electrical signals; and a frequency meter measures the frequency of a signal. Therefore, the correct option highlights the specific function of the combining device in measuring power, distinguishing it from tools that serve different purposes.