What we will do today: Investigate the two ways in which current moves around a circuit (a.c. and d.c.) State whether the mains supply is a.c. or d.c. State whether a battery supply is a.c. or d.c. Use an oscilloscope to see the patterns of a.c. and d.c. Look at energy changes in electronic components.

Electric current Electric current is sent round a circuit in two different ways: 1.Direct Current (d.c.): when electrons flow around a circuit in one direction. A battery supply is an example of d.c. 2.Alternating Current (a.c.): when electrons move both forwards and backwards in a circuit, changing direction many times in each second. The mains supply is an example of a.c.

The oscilloscope An oscilloscope is used to draw a graph of an electric signal. It shows the following patterns for d.c. and a.c.: d.c.a.c.

Revision of Energy Types MACHELPS M ovement (kinetic) A tomic C hemical H eat E lectrical L ight P otential S ound

Energy transformations: Whenever there is an electrical current in a component, there is an energy transfer. Electrical component Energy transformation Buzzer Electrical Energy → Motor Electrical Energy → Resistor Electrical Energy → Lamp Electrical Energy →

2005