Which of the following is used to measure horsepower? Tachometer Dynamometer Ammeter Ohmmeter

Horsepower is a unit of power used to measure the output of engines. Among the options provided:<br />1. A tachometer is an instrument that measures the rotation speed of a shaft or disk, as in a motor or other machine. It does not measure power.<br />2. A dynamometer is a device used to measure force. In the context of engines, it measures the power output of the engine, making it the correct answer.<br />3. An ammeter is an instrument for measuring electric current in amperes. It does not measure power.<br />4. An ohmmeter is an electrical measuring instrument that measures electrical resistance, the opposition to the flow of an electric current. It does not measure power.<br />Therefore, the correct answer is the dynamometer, which is used to measure horsepower.