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A resistance is connected to a capacitor...

A resistance is connected to a capacitor in AC are the phase differece is `(pi)/(4)` between current and voltage. Whe the same resistance is connected to an inductor, phase difference becomes `tan^(-1)(2)`. Power factor of the circuit when both capacitor and inductor are connect to the resistance will be

A

1

B

`(1)/(sqrt2)`

C

`(1)/(sqrt3)`

D

`(1)/(2)`

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The correct Answer is:
To solve the problem step by step, we will analyze the given information regarding the phase differences when a resistance is connected to a capacitor and an inductor, and then find the power factor when both are connected. ### Step 1: Understand the Phase Difference with the Capacitor When the resistance \( R \) is connected to a capacitor, the phase difference \( \phi_C \) is given as \( \frac{\pi}{4} \) (or 45 degrees). The power factor \( \cos(\phi_C) \) can be expressed as: \[ \cos\left(\frac{\pi}{4}\right) = \frac{R}{Z_C} \] where \( Z_C \) is the impedance of the circuit with the capacitor. ### Step 2: Calculate the Capacitive Reactance From the above equation, we can express the impedance \( Z_C \): \[ Z_C = \frac{R}{\cos\left(\frac{\pi}{4}\right)} = R \sqrt{2} \] Now, we know that: \[ Z_C = \sqrt{R^2 + X_C^2} \] where \( X_C \) is the capacitive reactance. Since \( Z_C = R \sqrt{2} \), we can set up the equation: \[ R \sqrt{2} = \sqrt{R^2 + X_C^2} \] Squaring both sides: \[ 2R^2 = R^2 + X_C^2 \] This simplifies to: \[ X_C^2 = R^2 \implies X_C = R \] ### Step 3: Understand the Phase Difference with the Inductor When the same resistance \( R \) is connected to an inductor, the phase difference \( \phi_L \) is given by: \[ \tan(\phi_L) = 2 \] This implies: \[ \tan(\phi_L) = \frac{X_L}{R} = 2 \implies X_L = 2R \] ### Step 4: Calculate the Impedance with Both Capacitor and Inductor When both the capacitor and inductor are connected to the resistance, the total impedance \( Z \) can be calculated using the formula: \[ Z = \sqrt{R^2 + (X_L - X_C)^2} \] Substituting the values of \( X_L \) and \( X_C \): \[ Z = \sqrt{R^2 + (2R - R)^2} = \sqrt{R^2 + R^2} = \sqrt{2R^2} = R\sqrt{2} \] ### Step 5: Calculate the Power Factor The power factor \( \text{PF} \) is given by: \[ \text{PF} = \frac{R}{Z} \] Substituting the value of \( Z \): \[ \text{PF} = \frac{R}{R\sqrt{2}} = \frac{1}{\sqrt{2}} \] ### Final Answer Thus, the power factor of the circuit when both the capacitor and inductor are connected to the resistance is: \[ \text{Power Factor} = \frac{1}{\sqrt{2}} \]
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