Electricity: Magnetic and Heating Effects
NoteWhat This Chapter Covers
Flick a switch and electric current does invisible work. This chapter reveals two of its hidden powers. First, the magnetic effect: a current-carrying wire behaves like a magnet — the surprising link between electricity and magnetism that Hans Christian Oersted stumbled upon in 1820, and which lets us build electromagnets strong enough to lift cars in a scrapyard. Second, the heating effect: current meeting resistance turns electrical energy into heat, the principle behind every electric heater, iron and kettle. Finally we open up the cell and battery to see how chemicals quietly make the current in the first place — from a lemon to a lithium-ion phone battery.
Learning Outcomes
By the end of this chapter, you will be able to:
- demonstrate the magnetic effect of electric current using a compass, and explain the idea of a magnetic field;
- build an electromagnet and explain how its strength and poles can be changed;
- describe real uses of electromagnets, including lifting electromagnets;
- explain the heating effect of electric current, the role of resistance, and why nichrome is used in heaters;
- describe how a Voltaic cell, a dry cell and a rechargeable battery generate electricity, and identify the electrodes and electrolyte.