If a positive charge is placed on the p-type side, the holes are pushed towards the junction. At the same time, electrons in n-type materials are attracted towards the junction. Since there is an abundance of carriers at the junction, current can flow through the junction from a power supply. However, if the charges placed on the semiconductor are reversed, the holes and electrons are pulled away from the junction, leaving a relatively non-conductive region of silicon that interrupts the flow of current. These can become more complicated by creating a third region, such as pnp or npn. This 3-way configuration is called a transistor.