Clamp ammeter is one of the measuring instruments commonly used by electricians. It is an instrument that measures the current value by putting a magnetic circuit that can be opened and closed on the current-carrying wire under test. The clamp ammeter is composed of a transformer (transformer) and an ammeter. The iron core of the transformer is made into a movable opening and is shaped like a clamp. The movable part is connected to the handle. When the handle is held tightly, the iron core of the current transformer opens. The measured current-carrying wire can be placed in the jaws to become the primary winding (primary coil) of the current transformer. When the jaws are closed, alternating magnetic flux passes through the iron core of the current transformer, and an induced current is generated in the secondary winding (secondary coil) of the transformer. The ammeter is connected to both ends of the secondary winding, and the current value indicated by its pointer is proportional to the working current of the clamped current-carrying wire, and the measured current value can be read directly from the dial. In middle school physics teaching, the application of the clamp ammeter as a transformer is introduced separately in the teaching materials. The clever use of the clamp ammeter for experimental exploration can effectively improve students' understanding of the laws of electromagnetic induction and the principle of transformers, and can effectively cultivate students to develop Caring about good habits of science, technology and society.
