Chapter 19: Problem 1
(I) Calculate the terminal voltage for a battery with an internal resistance of 0.900 \(\Omega\) and an emf of 6.00 V when the battery is connected in series with (\(a\)) a 71.0-\(\Omega\) resistor, and (\(b\)) a 710-\(\Omega\) resistor.
Short Answer
Expert verified
The terminal voltages are approximately 5.93 V for the 71-\(\Omega\) resistor and 5.99 V for the 710-\(\Omega\) resistor.
Step by step solution
01
Understanding the Problem
We need to calculate the terminal voltage of a battery with a given electromotive force (emf) and internal resistance when connected to resistors of different resistances. Terminal voltage is the voltage output of a battery at its terminals.
02
Formula for Terminal Voltage
The terminal voltage \( V \) of a battery can be calculated using the formula: \( V = \text{emf} - I \times r \), where \( \text{emf} \) is the electromotive force, \( I \) is the current through the circuit, and \( r \) is the internal resistance of the battery.
03
Calculate Current for Each Case
For each resistor, calculate the current \( I \) using Ohm's Law: \( I = \frac{\text{emf}}{R + r} \), where \( R \) is the resistance of the external resistor and \( r \) is the internal resistance.
04
Current Calculation for 71.0 \( \Omega \) Resistor
For \( R = 71.0 \Omega \), calculate the current: \( I = \frac{6.00}{71.0 + 0.900} \approx 0.083 \) A.
05
Terminal Voltage with 71.0 \( \Omega \) Resistor
Substitute \( I \) and \( r \) into the terminal voltage formula: \( V = 6.00 - 0.083 \times 0.900 \approx 5.93 \) V.
06
Current Calculation for 710 \( \Omega \) Resistor
For \( R = 710 \Omega \), calculate the current: \( I = \frac{6.00}{710 + 0.900} \approx 0.00843 \) A.
07
Terminal Voltage with 710 \( \Omega \) Resistor
Substitute \( I \) into the terminal voltage formula: \( V = 6.00 - 0.00843 \times 0.900 \approx 5.99 \) V.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Internal Resistance
When discussing batteries and circuits, internal resistance is a vital concept to grasp. Every battery has some resistance to the flow of electric current within itself, known as internal resistance, denoted as \( r \). This resistance is caused by the materials and processes inside the battery, which can impede the free flow of charge.Here’s why understanding internal resistance is important:
- It affects the actual voltage output of the battery, reducing the terminal voltage compared to its emf value.
- High internal resistance can cause the battery to heat up and reduce efficiency.
- The internal resistance can influence how much current flows through the circuit for a given load.
Ohm's Law
Ohm's Law is a fundamental principle in electronics, stating that the current \( I \) flowing through a conductor between two points is directly proportional to the voltage \( V \) across the two points, and inversely proportional to the resistance \( R \) of the conductor. The law is represented by the equation: \[ I = \frac{V}{R} \]In the context of this exercise, Ohm's Law allows us to determine the current flowing through a circuit when a battery is connected to an external resistor. For instance:
- When the external resistance is 71.0 \( \Omega \), the current is calculated by \( I = \frac{6.00}{71.0 + 0.900} \), leveraging both internal and external resistances.
- Similarly, with 710 \( \Omega \), it becomes \( I = \frac{6.00}{710 + 0.900} \), showcasing how variations in resistance influence current.
Electromotive Force (emf)
Electromotive force, often shortened to emf, and symbolized as \( \epsilon \), is the total energy supplied per charge by a source to drive a current around a complete circuit. Unlike terminal voltage, which accounts for losses due to internal resistance, emf is the ideal voltage value of a battery when no current flows, or when it’s not connected to any load.Why is emf important?
- It's the upper limit of potential energy a battery can provide. This sets a starting point for evaluating actual terminal voltage.
- Emf helps estimate the theoretical maximum efficiency of a battery since no energy is lost inside the battery when no current is drawn.
- In calculations, it gives a reference to determine how much voltage "drops" due to internal resistance when current is flowing.