An electric current is a flow of charged particles, such as electrons or ions, through an electrical conductor or space. It is defined as the net rate at which electric charge flows through a surface. The moving particles are called charge carriers, which may be of several types, depending on the conductor. In electric circuits, the charge carriers are often electrons moving through a wire. In semiconductors, the charge carriers can be electrons or holes. In an electrolyte, the charge carriers are ions, while in plasma- an ionized gas- they are also ions and electrons.