As I'm reading a course on electricity, this one says that an ammeter should be branched inline and not on a bridge. Can someone explain to me physically why we branch a amperemeter inline and a voltmeter on a branch?
The ammeter measure the current flowing through itself. If you want to measure the current flowing through another component, then you must make the current through the ammeter equal to the current through the component. If you wire it in series, that's true. If you wired it in parallel, the current would be unevenly divided between the component and the ammeter.
Similarly: The voltmeter measures the voltage across itself. If you want to measure the voltage across some other component, you must make the two voltages equal. If you wire it in parallel, that's true. If you wired it in series, the voltage would be unevenly divided between the component and the voltmeter.