How does connecting an electric device to a battery produce an current in the device?

Answer 1

If we connect a battery to a device and complete a circuit, current will flow in that circuit and through the device. A battery (in good condition) is an electrical storage device. Most of the ones we are familiar with are chemical cells. There are chemicals inside that would like to react, but cannot unless there is an external circuit through which electrons can move to get from one electrode in the battery to the other. The potential chemical energy in a battery can be converted into electrical energy by completing that circuit. There is a force called voltagethat arises between the electrodes of the battery. And this voltage (electromotive force, or EMF) is the way that the chemical potential energy expresses itself. Because the battery can convert chemical potential energy into electricity owing to that EMF between the electrodes, connecting a circuit across the battery will allow current to flow as the chemical reactions in the battery proceed. A very rough analogy can be drawn by looking at gravitational potential energy. If a Bowling ball is sitting on the floor and it is lifted onto a table, its gravitational potential energy has been increased. This is distantly similar to the chemical reactions that want to occur in the battery; they are potential energy, too. If the bowling ball rolls off the edge of the table, the potential energy is converted into kinetic energy by gravity. When we hook up an external circuit to the battery, the chemical potential energy (expressed as voltage) drives electrical current through that circuit and the device in it. The circuit here is composed of conductors and the device. Electrons in the conductors are hanging around in the conduction band, and if a voltage is applied, those electrons will begin moving in response. The device must be conductive to some extent, and it, too, will have this electron current flowing through it. The battery has been connected to a circuit and drives current through that circuit. The chemical potential energy in the battery is converted into electrical energy in the circuit and the device connected to it.

Answer 2

When you connect an electric device to a battery, the battery creates a voltage difference between its terminals. This voltage difference causes electrons to flow through the device's circuit, creating an electric current that powers the device. The current flows from the battery's positive terminal, through the device, and back to the negative terminal, completing the circuit.