A wire that warms up

The idea

Resistance converts some electrical energy into heat energy, so a conductor gets heated when current passes through it; this is the heating effect of electric current.

Touch the wire

A nichrome wire is joined to a cell. After some time you touch it.

What do you think it feels like?

• Warm
• Cold as ice
• It gives sparks

Let the current flow

Slide the time to the right. Watch the warmth bar.

Electrical energy to heat

While the current flowed, the wire got warmer. The resistance of the wire changed some electrical energy into heat energy.

Resistance converts some electrical energy into heat energy, so a conductor gets heated when current passes through it. This is the heating effect of electric current.

Notes

Resistance converts some electrical energy into heat energy. This warming is the heating effect of electric current.

Check yourself

When current passes through a conductor, it gets …

Which energy is changed into heat energy in a current carrying wire?

What causes the wire to get warm when current flows?

The warming of a conductor when current passes through it is called the …

• magnetised and cold. The heating effect is that the conductor warms up.
• frozen. The conductor warms. It does not freeze.
• heated — correct. Yes!
• Some of the electrical energy — correct. Yes!
• The energy of the compass needle. A compass has no part in it. Some electrical energy turns into heat.
• All the heat of the room. The heat is made in the wire. It is not taken from the room.
• The colour of the wire. Colour has no part. Resistance changes electrical energy into heat.
• The resistance of the wire — correct. Yes!
• A compass kept nearby. A compass only detects a magnetic field. Resistance makes the heat.
• magnetic effect of electric current. That is the effect in which a current produces a magnetic field.
• cooling effect of electric current. There is no such effect in this chapter.
• heating effect of electric current — correct. Yes!