The error caused by pressure coil inductance ina)capacitor across a pa...
To reduce the error in the wattmeter reading due to pressure coil inductance, the wattmeters are compensated by connecting a capacitor in parallel with a portion of series resistance (multiplier) as shown below.
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The error caused by pressure coil inductance ina)capacitor across a pa...
The error caused by pressure coil inductance in a pressure coil circuit is a result of the presence of a capacitor across a part of series resistance in the circuit. Let's understand why this is the correct option.
1. Introduction:
When an inductor, such as a pressure coil, is connected in series with a resistance, it forms an RL circuit. In this circuit, the inductance of the coil plays a significant role in determining the circuit's behavior.
2. Inductor Behavior:
An inductor opposes changes in current flowing through it by inducing an electromotive force (EMF) in the opposite direction. This property is described by the equation V = L(di/dt), where V is the voltage across the inductor, L is the inductance, and (di/dt) is the rate of change of current.
3. Capacitor Behavior:
A capacitor, on the other hand, stores energy in an electric field. It opposes changes in voltage across it by supplying or absorbing charge. The relationship between the voltage and charge on a capacitor is given by Q = CV, where Q is the charge, C is the capacitance, and V is the voltage across the capacitor.
4. Capacitor-Inductor Interaction:
When a capacitor and an inductor are connected in the same circuit, their behavior can interact with each other. This interaction is characterized by the resonant frequency of the circuit.
5. Effect on Pressure Coil Circuit:
In the given options, only option 'A' involves a capacitor across a part of series resistance in the pressure coil circuit. When a capacitor is connected in parallel with a part of the series resistance, it forms a parallel RC circuit with the pressure coil.
6. Resonant Frequency:
The parallel RC circuit has a resonant frequency given by the equation f = 1 / (2π√(LC)), where f is the resonant frequency, L is the inductance of the pressure coil, and C is the capacitance.
7. Error Caused:
At the resonant frequency, the impedance of the parallel RC circuit becomes very low, allowing more current to flow through the capacitor and bypassing the pressure coil. This can lead to inaccuracies in the measurement or control system where the pressure coil is used.
8. Conclusion:
Therefore, the error caused by pressure coil inductance in a pressure coil circuit is due to the presence of a capacitor across a part of series resistance in the circuit. This parallel RC circuit can create a low impedance path for current, bypassing the pressure coil and causing errors in the system.
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