Which of the following device works on the principle that the charge between the two flow if they are connected by a conducting wire:AVan de Graff generatorBPotentiometerCAmmeterDGalvanometer

The device that works on the principle that charge flows between two points if they are connected by a conducting wire is an Ammeter.

Here's why:

A. Van de Graff generator: This device works on the principle of electrostatic induction and mechanical separation of charge. It doesn't require a flow of charge through a wire.

B. Potentiometer: This device measures the electromotive force of a given cell, potential difference across a resistor, or internal resistance of a cell. It doesn't work on the principle of charge flow through a wire.

C. Ammeter: This device is used to measure the current in a circuit, and it works on the principle that charge flows between two points if they are connected by a conducting wire. Therefore, the answer is Ammeter.

D. Galvanometer: This device is used to detect and measure small amounts of current in an electrical circuit. It doesn't work on the principle of charge flow through a wire.