query: Who first measured magnetic force?
passage: Magnetic field
Three discoveries challenged this foundation of magnetism, though. First, in 1819, Hans Christian Ørsted discovered that an electric current generates a magnetic field encircling it. Then in 1820, André-Marie Ampère showed that parallel wires with currents attract one another if the currents are in the same direction and repel if they are in opposite directions.[7] Finally, Jean-Baptiste Biot and Félix Savart discovered the Biot–Savart law in 1820, which correctly predicts the magnetic field around any current-carrying wire.
passage: Lorentz force velocimetry
The use of magnetic fields in flow measurement date back to 19th century, when in 1832 Michael Faraday attempted to determine the velocity of the River Thames. Faraday applied a method in which a flow (the river flow) is exposed to a magnetic field (earth magnetic field) and the induced voltage is measured using two electrodes across the same flow. This method is the basis of the one of the most successful commercial applications in flow metering known as the inductive flowmeter. The theory of such devices has been developed and comprehensively summarized by Prof. J. A. Shercliff in early 1950s. While inductive flowmeters are widely used for flow measurement in fluids at room temperatures such as beverages, chemicals and waste water, they are not suited for flow measurement of media such as hot, aggressive or for local measurements where surrounding obstacles limit access to the channel or pipe. Since they require electrodes to be inserted into the fluid, their use is limited to applications at temperatures far below the melting points of practically relevant metals.