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igcse physics notesprinted 107 路 PDF 107
124 pagesrevision 46936
printed 107 路 PDF 107
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107
Transformer
A transformer consists of two coils wrapped around a soft iron core and is
used to transform voltages,
Electromagnetic induction is the working principle of a transformer.
Alternating current in the primary coil creates a changing magnetic field;
this changing magnetic field links with the secondary coil and induces an
alternating emf in it.
A step up transformer has more turns on the secondary coil and the voltage
of the secondary coil is greater than that of the primary. A step down
transformer has more turns on the primary coil and the voltage of the
primary coil is greater than that of the secondary.
Transformer equation:
饾憶饾憸 饾憸饾憮 饾憽饾憿饾憻饾憶饾憼 饾憸饾憮 饾憹饾憻饾憱饾憵饾憥饾憻饾懄
饾憶饾憸 饾憸饾憮 饾憽饾憿饾憻饾憶饾憼 饾憸饾憮 饾憼饾憭饾憪饾憸饾憶饾憫饾憥饾憻饾懄=
饾憹.饾憫 饾憸饾憮 饾憹饾憻饾憱饾憵饾憥饾憻饾懄
饾憹.饾憫 饾憸饾憮 饾憼饾憭饾憪饾憸饾憶饾憫饾憥饾憻饾懄
For a 100% efficient transformer, because power used is constant:
饾惣饾憙饾懀饾憹=饾惣饾憼饾懀饾憼
Transformers are used to step up voltage in power lines which reduces
power loss:
High voltage, low current
Low voltage, high current
This is because a higher voltage means a smaller current and loss of
power d8ue to P=I^2R will be lower