Alternating and direct current
This revision bite will take you through the subject areas: battery and mains supplies, symbols and circuits, charge and current, and voltage and energy.
Work through them all or go to the ones that interest you. You may wish to print a hard copy for your reference.
Cells, batteries and the mains supply are all sources of electrical energy. There are some important differences between them that you should know about:
Cells and batteries supply direct current (dc). This means that the current is always in the same direction in a circuit.
Video: Direct current vs alternating current
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