Chapter 27: Problem 43
You are given a number of \(10 \Omega\) resistors, each capable of dissipating only \(1.0 \mathrm{~W}\) without being destroyed. What is the minimum number of such resistors that you need to combine in series or in parallel to make a \(10 \Omega\) resistance that is capable of dissipating at least \(5.0 \mathrm{~W}\) ?
Short Answer
Step by step solution
Understand Power Dissipation in Resistors
Determine the Total Current Requirement
Calculate the Minimum Parallel Resistor Count
Verify the Configuration's Resistance
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power Dissipation
- For a \(10 \Omega\) resistor capable of dissipating a maximum of \(1.0\) watt, the maximum allowable current can be found as \( I = \sqrt{\frac{P}{R}} \).
- In this scenario, the current should not exceed \(0.316 \) amperes to avoid damaging the resistor.
- Power dissipation varies with the square of the current, meaning a small increase in current can significantly elevate the dissipation.
Series and Parallel Circuits
- Series Circuits: In a series configuration, resistors are connected end-to-end. The total resistance \( R_{total} \) is simply the sum of individual resistances \( R_1 + R_2 + \, \ldots\, \ R_n \). The current in a series circuit remains constant through all components. This type of connection was not ideal for our problem since we had to handle larger current without increasing resistance beyond \(10 \Omega\).
- Parallel Circuits: In a parallel configuration, resistors are connected across the same two points. The equivalent resistance \( R_{eq} \) can be calculated using the reciprocal formula: \( \frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \,\ldots\,+ \frac{1}{R_n} \). This configuration allows the circuit to carry a higher total current, as the current is divided among the parallel paths.
Ohm's Law
- By rearranging Ohm's Law, you can solve for any one of the three variables if the other two are known. For instance, \( I = \frac{V}{R} \), or \( R = \frac{V}{I} \).
- In our exercise, knowing the resistance (\(10 \Omega\)) and applying Ohm's Law helped us determine the necessary conditions for current and power dissipation.