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A conducting wire of uniform cross secti...

A conducting wire of uniform cross section, having resistance R is bent to form a circle. O is the centre of this circle. Two points P and Q are selected on the ring in such a manner that `anglePOQ` is `theta`. If a battery of emf E and negligible internal resistance is connected between P and Q, then the current drawn from the battery would be

A

`(E theta)/(4 pi^(2) R (2 pi - theta))`

B

`(E (2 pi - theta))/(4 pi^(2) theta R)`

C

`(4 pi^(2) E theta)/(R(2 pi - theta))`

D

`(4 pi^(2) E)/(theta R(2 pi - theta))`

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The correct Answer is:
To solve the problem, we need to find the current drawn from a battery connected between two points P and Q on a circular conducting wire of resistance R. The angle subtended by points P and Q at the center O of the circle is θ. ### Step-by-Step Solution: 1. **Understanding the Wire and Resistance**: - The wire is bent into a circle, and its total resistance is R. - The circumference of the circle is given by \( C = 2\pi L \), where L is the length of the wire. - The resistance per unit length of the wire is \( \frac{R}{2\pi L} \). 2. **Finding the Length of Arc PQ**: - The length of the arc PQ, which subtends an angle θ at the center, is given by: \[ L_{PQ} = L \cdot \theta \] 3. **Calculating the Resistance R1 between Points P and Q**: - The resistance \( R_1 \) corresponding to the arc PQ can be calculated as: \[ R_1 = \text{Resistance per unit length} \times \text{Length of arc PQ} = \frac{R}{2\pi L} \cdot (L \cdot \theta) = \frac{R \theta}{2\pi} \] 4. **Finding the Length of the Remaining Arc**: - The remaining arc, which is the arc opposite to PQ, subtends an angle \( 2\pi - \theta \) at the center O. - The length of this arc is: \[ L_{remaining} = L(2\pi - \theta) \] 5. **Calculating the Resistance R2 of the Remaining Arc**: - The resistance \( R_2 \) for the remaining arc can be calculated as: \[ R_2 = \frac{R}{2\pi L} \cdot (L(2\pi - \theta)) = \frac{R(2\pi - \theta)}{2\pi} \] 6. **Finding the Equivalent Resistance (R_eq)**: - Since \( R_1 \) and \( R_2 \) are in parallel, the equivalent resistance \( R_{eq} \) can be calculated using the formula: \[ \frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} \] - Substituting the values of \( R_1 \) and \( R_2 \): \[ \frac{1}{R_{eq}} = \frac{2\pi}{R\theta} + \frac{2\pi}{R(2\pi - \theta)} \] 7. **Simplifying the Expression**: - To find \( R_{eq} \), we can simplify: \[ R_{eq} = \frac{R\theta(2\pi - \theta)}{2\pi} \] 8. **Calculating the Current (I)**: - Using Ohm's law \( V = IR \), where \( V \) is the EMF \( E \): \[ I = \frac{E}{R_{eq}} = \frac{E}{\frac{R\theta(2\pi - \theta)}{2\pi}} = \frac{2\pi E}{R\theta(2\pi - \theta)} \] ### Final Answer: The current drawn from the battery is: \[ I = \frac{2\pi E}{R\theta(2\pi - \theta)} \]

To solve the problem, we need to find the current drawn from a battery connected between two points P and Q on a circular conducting wire of resistance R. The angle subtended by points P and Q at the center O of the circle is θ. ### Step-by-Step Solution: 1. **Understanding the Wire and Resistance**: - The wire is bent into a circle, and its total resistance is R. - The circumference of the circle is given by \( C = 2\pi L \), where L is the length of the wire. - The resistance per unit length of the wire is \( \frac{R}{2\pi L} \). ...
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MODERN PUBLICATION-CURRENT ELECTRICITY-Objective Type Questions (MULTIPLE CHOICE QUESTIONS) (A. MULTIPLE CHOICE QUESTIONS WITH ONLY ONE CORRECT ANSWER)
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