What can an ammeter read?

An ammeter is an instrument that measures the current flowing in a circuit, typically in amperes. The correct answer about what an ammeter can read is related to its ability to detect the effects that an electric current produces, which includes understanding the conductor's magnetic field. When current flows through a wire, it generates a magnetic field around the conductor. This principle is foundational to the operation of many electrical devices, including the ammeter itself, which can sometimes utilize the magnetic properties related to the flow of current for measurement.

The other options involve measurements that fall outside the capabilities of an ammeter. For instance, pressure drop refers to a difference in pressure across a fluid or gas flow system, which is measured by pressure gauges rather than ammeters. Load in parallel wires pertains to the distribution of electrical loads in a network, which require different instruments to measure how power is shared among parallel circuits. Lastly, direct power across loads involves measuring voltage and current to determine the power consumed, which is a function of both voltage and current, typically assessed with a wattmeter rather than an ammeter alone. Thus, among the choices, the reading of the conductor magnetic field directly relates to the current flow measured by an ammeter.