Transformer ratios , Wattage rating , Component symbols (BS 3939)and RL time constants.

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Transformer ratios

The ratio of a transformer refers to the ratio of the number of turns in one winding to the number of turns in the other winding. To avoid confusion it is always desirable to state in which sense the ratio is being expressed: e.g. the ‘primary-to-secondary’ ratio n^/n^ The turns ratio is related to the impedance ratio thus:

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where np = number of primary turns, ns = number of secondary turns, Zp = impedance of primary (ohms), and Zs = impedance of secondary (ohms).

Wattage rating

If resistance and current values are known:

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Wavelength of tuned circuit

Formula for the wavelength in metres of a tuned oscillatory circuit is:

1885 VLC

where L = inductance in microhenries and C = capacitance in microfarads.

Decimal multipliers

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Reactance of capacitors at spot frequencies

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Reactance of inductors at spot frequencies

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RC time constants

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RL time constants

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Component symbols (BS 3939)

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