Early wattmeter on display at the Historic Archive and Museum of Mining in, The traditional analog wattmeter is an instrument. The device consists of a pair of fixed, known as current coils, and a movable coil known as the potential coil. The current coils are connected in with the circuit, while the potential coil is connected in. Also, on wattmeters, the potential coil carries a needle that moves over a scale to indicate the measurement. A current flowing through the current coil generates an around the coil. The strength of this field is proportional to the line current and in phase with it. Griffiths Introduction To Electrodynamics PdfThe potential coil has, as a general rule, a high-value connected in series with it to reduce the current that flows through it. The result of this arrangement is that on a circuit, the deflection of the needle is proportional to both the ( I) and the ( V), thus conforming to the equation P= VI. How to program sky hd remote to panasonic tv. For, current and voltage may not be in phase, owing to the delaying effects of circuit. On an circuit the deflection is proportional to the average instantaneous product of voltage and current, thus measuring, P= VI cos φ. Here, cos φ represents the which shows that the power transmitted may be less than the apparent power obtained by multiplying the readings of a and in the same circuit. The two circuits of a wattmeter can be damaged by excessive current.
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