Magnetism & Electromagnetism - 7.3.2 Uses of the Generator Effect (HT Only) (GCSE Physics AQA)

Uses of the Generator Effect (HT Only)

Dynamos and Alternators

• We have already seen in a previous tutorial that the generator effect creates current. It does so by moving a wire inside a magnetic field, or by moving a magnet in a coil of wire.
• The current that is produced by a dynamo can be ac or dc. AC stands for alternating current, whilst dc stands for direct current and these types of current are produced in different ways.
• Alternators will produce alternating current and dynamos will produce direct current. Both of these devices will use a rotating coil to generate the current.

Differences Between the Two

• Inside an alternator, there is a coil rotating inside a magnetic field which generates the current. The current is known as an alternating current since it changes direction every half turn. This is due to the slip rings and brushes.
• Inside a dynamo, there is also a coil rotating inside a magnetic field which generates the current. The current is known as a direct current since it does not change direction. This is due to the presence of a split ring commutator.

Drawing and Interpreting Graphs

For AQA exams, it is important that you are able to draw and interpret graphs relating to potential difference.

We will be looking at the potential difference generated in a coil against time.

To measure the pd generated by a coil, we can use an oscilloscope as shown below. This will be connected to the circuit with the generator in question.

• For an AC generator, the pd and current produced will both be alternating. This means that the trace on the oscilloscope will appear in both the positive and negative halves.
• For a DC generator, the pd and current produced will both be direct. This means that the trace on the oscilloscope will only appear in the positive half, not in the negative half.