When a motor runs directly from the mains, it draws a load current which supplies the torque, and a magnetising, or reactive current that develops the magnetic field. This current flows back and forth in the motor and cables, but does no useful work, and in small installations is not metered or paid for. The ratio between the total and reactive current is known as the power factor. Many other loads also draw reactive currents, so it makes sense to minimise and correct the power factor if possible. Power factor correction equipment can be used in larger installations.