Abstract
For the measurement of power in d.c. circuits a wattmeter is not necessary since power is then the product of ammeter and voltmeter readings. For the a.c. circuit this is only true if the power factor is unity, and for all other conditions a wattmeter is essential since such an instrument indicates true power, that is
supply voltage × current × cosine of phase angle between voltage and current
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© 1976 A. Simpson
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Simpson, A. (1976). Measurement of Power and Energy. In: Testing Methods and Reliability — Power. Palgrave, London. https://doi.org/10.1007/978-1-349-02629-6_7
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DOI: https://doi.org/10.1007/978-1-349-02629-6_7
Publisher Name: Palgrave, London
Print ISBN: 978-1-349-02631-9
Online ISBN: 978-1-349-02629-6
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