When electricity flows through the air from one pole of an electric circuit to another, or jumps from its source to ground without flowing through a desired circuit, it is said to arc. This phenomenon is often accompanied by visible flashes of light and a crackling noise. Lightning and static electricity shocks are well-known examples of arcing. In electrical generation, arcing is usually undesirable because an arc sends all electricity to ground without putting it to a practical use. However, deliberately-created high-intensity arcs of electricity have many practical applications ranging from welding to high-intensity lighting.