Heating is unavoidable

The idea

Heat generation is an inevitable consequence of electric current; it is often undesirable, converting useful electrical energy into heat and raising the temperature of circuit components, which can alter their properties.

Warm wires

A current is flowing in the wires and components of a radio. After some time they are a little warm, although the radio was not built to make heat.

Why do the components get warm?

• Heat generation is an unavoidable result of electric current in a conductor
• The radio was built to heat the room
• Heat is made when something is wrong with the radio

Wanted or unwanted

Drag or tap each example into the group where it belongs.

Always some heat

Whenever a current flows in a conductor some heat is produced. In a heater that is the whole purpose. In many other cases it wastes useful electrical energy and warms the parts.

Heat generation in a conductor is an inevitable consequence of electric current. It is often undesirable, as it converts useful electrical energy into heat and raises the temperature of circuit components, which can alter their properties.

Notes

Heat generation is an inevitable consequence of electric current; it is often undesirable, converting useful electrical energy into heat and raising the temperature of components, which can alter their properties.

Check yourself

What is true of the heat generated in a conductor that carries a current?

Why is the heating of a conductor often undesirable?

What can the unavoidable heating do to the components of a circuit?

Which device is based on Joule's heating?

• It is produced only in heaters. Heat is generated in any conductor carrying a current. Heaters are just the devices that make use of it.
• It can be avoided completely by using thicker wires. The generation of heat in a conductor is an inevitable consequence of electric current.
• It is an inevitable consequence of the current — correct. Yes!
• It converts useful electrical energy into heat — correct. Yes!
• It makes the current flow faster. Heat does not speed up the current. It turns useful electrical energy into heat.
• It creates new electrons. Heating does not create electrons. It converts useful electrical energy into heat.
• Make them lose all their mass. The book says it can increase the temperature of the components and alter their properties.
• Raise their temperature and alter their properties — correct. Yes!
• Nothing at all. Unavoidable heating can increase the temperature of the components and alter their properties.
• An ammeter. An ammeter measures current. The electric kettle is one of the familiar devices based on Joule's heating.
• A switch. A switch only makes or breaks a connection. The electric kettle is one of the familiar devices based on Joule's heating.
• An electric kettle — correct. Yes!