How does a galvanometer detect electric currents?

A galvanometer functions by detecting the magnetic effect of electric currents. When current flows through a coil of wire positioned within a magnetic field, it generates a magnetic force that causes the coil to experience a torque. This results in the coil's movement, usually indicated by a pointer moving over a calibrated scale. This movement translates directly to the strength of the current flowing through the coil, allowing the galvanometer to provide an indication of the current's presence and magnitude.

The other options do not apply to how a galvanometer operates. For instance, measuring temperature changes is not related to current detection; instead, temperature is affected by power loss or resistance heating, not the magnetic effect of current. Voltage fluctuations pertain to the electric potential difference and are not directly indicative of current flow in the way a galvanometer detects it. Similarly, calculating resistance involves utilizing Ohm's law, which does not involve the detection of current itself but rather the relationship between voltage and current when a current is already known or measured. Thus, the most accurate description of how a galvanometer works is through the detection of the magnetic effect of the current.