If the polarity is reversed in a meter bridge, then the measurements taken by the bridge will be incorrect. This is because the bridge relies on the current running through the circuit in order to measure the resistance of the circuit. If the polarity is reversed, then the current will run in the opposite direction, resulting in incorrect measurements.

Non-ohmic resistors are resistors that do not obey Ohm's law, meaning their resistance does not depend linearly on the applied voltage. Examples include thermistors, photoresistors, tunnel diodes, and field-effect transistors. A galvanometer is a device used to measure electric current. It can be converted into an ammeter by connecting a low resistance in series with the galvanometer. This resistance should be low enough that it does not significantly affect the current being measured, but...

The Wheatstone bridge is not suitable for measuring very low resistance because it is based on a ratio of two resistances, and the resolution of the bridge decreases as the ratio approaches 1. This means that the Wheatstone bridge is not accurate enough to measure very small changes in resistance.

No, an ammeter is not a low-resistance galvanometer. An ammeter is an instrument used to measure electric current, while a low-resistance galvanometer is a device used to detect small electric currents. The two instruments measure different parameters and thus require different designs. An ammeter typically has a very low resistance, while a low-resistance galvanometer has a much higher resistance.