This document entails comprehensive information about AC and DC power and motors and generators, including definitions, diagrams and additional information to ensure a thorough understanding of the concepts. All of the information needed to calculate the answers to the difficult questions in examin...
ALTERNATING CURRENT
Voltage vs Time & Current vs Time
Reducing the emf of a current
Advantages of Alternating Current
IMPORTANT CONCEPTS DC MOTORS, AC GENERATORS
& DC GENERATORS
Table comparing Energy conversion, Type of Current
used/produced, Structure, Function & Rules/Laws
applied and uses
Exam Guidelines
ALTERNATING CURRENT
AC generators produce an alternating current due to the fact that the current induced in the
coil/wires inside the generator is continuously changing direction and size. This change is best
illustrated in the Current vs time graph below:
Current vs Time Sine Graph
, 2
The peaks in the current (both positive & negative) correspond to where the coil is moving at
90° to the magnetic field.
When the coil is moving parallel to the magnetic field the current is ZERO.
The Voltage vs Time Graph (also a Sine Graph)
South Africa’s electricity supply ranges between 220 V and 240 V (these values are not the
maximum values of the voltage produced, but are statistical averages of the voltage
supplied).
This statistical average is described as the Root Mean Square or rms value.
The Vrms (root mean square voltage) is smaller than the maximum voltage by a factor of
and has the following equation:
Vrms =
Graphical representation follows below:
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