Today, however, crucial words used to describe these traditional topics have been stripped from an influential children's dictionary in favour of more 'modern' terms. Among the entries which have disappeared from the latest edition of the Oxford Junior Dictionary are disciple, coronation, empire, piglet and acorn. In their place come the likes of MP3 player, broadband, biodegradable, committee and celebrity.
A heat pump is a device that transfers heat energy from a source of heat to a destination called a heat sink. Heat pumps are designed to move thermal energy in the opposite direction of spontaneous heat transfer by absorbing heat from a cold space and releasing it to a warmer one. A heat pump uses a small amount of external power to accomplish the work of transferring energy from the heat source to the heat sink.
A heat pump is an air conditioner in which the refrigeration cycle can be reversed, producing heating instead of cooling in the indoor environment. They are also commonly referred to as a reverse cycle air conditioner. The heat pump is significantly more energy efficient than electric resistance heating.