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Alternating Current

Practice Questions:

Question 1: easy

In pure inductive circuit, the curves between frequency f and reciprocal of inductive reactance 1/XL is :

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Question 2: easy

In an LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An emf E = E0 cos (wt) applied to the circuit. The power consumed in the circuit is :

1. \[\frac{E_{0}^{2}}{R}\]

2. \[\frac{E_{0}^{2}}{2R}\]

3. \[\frac{E_{0}^{2}}{4R}\]

4. \[\frac{E_{0}^{2}}{8R}\]

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Question 3: easy

Which one of the following curves represents the variation of impedence (Z) with frequency f in series LCR circuit :-

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Question 4: easy

In series LCR circuit voltage across L, C & R is 20V each. If capacitor is short-circuited then
voltage across inductor is :

1. 20 V

2. 20√2 V

3. 10√2 V

4. 10 V

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Question 5: easy

A coil has power factor of 0.707 at 60 Hz. Then its power factor at 180 Hz will be :-

1. \[\frac{1}{\sqrt{2}}\]

2. \[\frac{1}{\sqrt{5}}\]

3. \[\frac{1}{\sqrt{10}}\]

4. \[\sqrt{\frac{5}{2}}\]

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Question 6: easy

A variable inductor is connected to an ac source. What effect does increasing the inductance have on the reactance and current in this circuit ?

1. Reactance - Decreases, Current - No change

2. Reactance - Increases, Current - Increases

3. Reactance - Decreases, Current - Increases

4. Reactance - Increases, Current - Decreases

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Question 7: easy

A variable capacitor is connected to an ac source. What effect does decreasing the capacitance have on the reactance and current in this circuit ?

1. Reactance - Decreases, Current - No change

2. Reactance - Increases, Current - Increases

3. Reactance - Decreases, Current -Increases

4. Reactance - Increases, Current -Decreases

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