Electricity is the movement of charged particles, usually electrons, from one place to another. Materials that electricity can move through easily are called conductors. Most metals, such as iron, copper and aluminum (you left this answer blank), are good conductors (you left this answer blank) of electricity. Other materials, such as rubber, wood and glass, block the flow of electricity. Materials which prevent (you left this answer blank) the flow of electricity are called insulators. Electrical cords are usually made with both conductors and insulators (you left this answer blank). Electricity flows through a conductor (you left this answer blank) in the center of the cord. A layer of insulation surrounds (you left this answer blank) the conductor and prevents (you left this answer blank) the electricity from 'leaking' out.