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A cell of emf epsilon and internal resis...

A cell of emf `epsilon` and internal resistance `r` drives a current `i` through an extermal resistance `R`
(i) The cell suppllied `epsilon i` power
(ii) Heat is produced in `R` at the rate `epsilon i`
(iii) Heat is produced in `R` at the rate `epsilon I ((R )/(R+r))`
(iv) Heat is produced in the cell at the rate `epsilon i(r /(R+r))`

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The correct Answer is:
To solve the problem, we need to analyze the power supplied by the cell, the heat produced in the external resistance \( R \), and the heat produced in the internal resistance \( r \) of the cell. ### Step-by-Step Solution: 1. **Power Supplied by the Cell**: The power supplied by the cell can be expressed as: \[ P_{\text{supplied}} = \epsilon i \] where \( \epsilon \) is the EMF of the cell and \( i \) is the current flowing through the circuit. **Hint**: Remember that the total power supplied by the cell is the product of EMF and the current. 2. **Power Dissipated in the External Resistance \( R \)**: The heat produced in the external resistance \( R \) is given by Joule's law: \[ P_R = i^2 R \] This represents the rate of heat produced in the resistor due to the current flowing through it. **Hint**: Use the formula \( P = I^2 R \) to find the power dissipated in the resistor. 3. **Power Dissipated in the Internal Resistance \( r \)**: The power dissipated in the internal resistance of the cell is: \[ P_r = i^2 r \] This is the heat produced in the internal resistance due to the current flowing through it. **Hint**: Similar to the external resistance, apply \( P = I^2 R \) for the internal resistance as well. 4. **Total Power Supplied**: The total power supplied by the cell is used to overcome both the external and internal resistances: \[ P_{\text{total}} = P_R + P_r = i^2 R + i^2 r = i^2 (R + r) \] Thus, we can express the current \( i \) in terms of \( \epsilon \) and the resistances: \[ i = \frac{\epsilon}{R + r} \] **Hint**: The total power supplied by the cell equals the sum of the power dissipated in both resistances. 5. **Heat Produced in the External Resistance \( R \)**: Substituting \( i \) in the expression for \( P_R \): \[ P_R = i^2 R = \left(\frac{\epsilon}{R + r}\right)^2 R = \frac{\epsilon^2 R}{(R + r)^2} \] **Hint**: Substitute the expression for current \( i \) into the power formula for the external resistance. 6. **Heat Produced in the Internal Resistance \( r \)**: Similarly, substituting \( i \) in the expression for \( P_r \): \[ P_r = i^2 r = \left(\frac{\epsilon}{R + r}\right)^2 r = \frac{\epsilon^2 r}{(R + r)^2} \] **Hint**: Again, substitute the expression for current \( i \) into the power formula for the internal resistance. ### Conclusion: From our analysis, we can conclude that: - The power supplied by the cell is \( \epsilon i \). - The heat produced in the external resistance \( R \) is \( \frac{\epsilon^2 R}{(R + r)^2} \). - The heat produced in the internal resistance \( r \) is \( \frac{\epsilon^2 r}{(R + r)^2} \). Thus, the correct options based on the statements provided in the question are: - (iii) Heat is produced in \( R \) at the rate \( \epsilon i \frac{R}{R+r} \). - (iv) Heat is produced in the cell at the rate \( \epsilon i \frac{r}{R+r} \).
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RESONANCE ENGLISH-CURRENT ELECTRICITY-Exercise-2 (Part-3)
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