Everything Science Grade 12

13.2 CHAPTER 13. ELECTRODYNAMICS

In an AC generator the two ends of the coil areeach attached to a slip ring that makes

contact with brushes asthe coil turns. The direction of the current changes with every

half turn of the coil. Asone side of the loop moves to the other pole ofthe magnetic

field, the current in theloop changes direction.The two slip rings of theAC generator

allow the coil to turn without breaking the connections to the load circuit. This type of

current which changes direction is known as alternating current.

FACT

AC generators are also
known as alternators.
They are found in mo-
tor cars to charge the car
battery.

DC generator ESCFS

A simple DC generatoris constructed the sameway as an AC generator except that

there is one slip ring which is split into two pieces, called a commutator, so the current

in the external circuit does not change direction.The layout of a DC generator is shown

in Figure 13.4. The split-ring commutator accommodates for the change in direction

of the current in the loop, thus creating direct current (DC) current going through the

brushes and out to the circuit.

N S

split ring

brush brush

load

split ring commutator

Figure 13.4: Layout of adirect current generator.

The shape of the emf from a DC generator is shown in Figure 13.5. The emf is not

steady but is the absolute value of a sine/cosinewave.