CH 7: Power, Energy
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Questions and Answers

What is the definition of power according to the text?

  • The resistance to the flow of electric current
  • The rate at which work is done or energy is transferred over time (correct)
  • The rate at which energy is generated
  • The amount of energy consumed by a device

    • Which formula is used to calculate power in electrical circuits when voltage (V) and current (I) are known?

  • $P = V^2/R$
  • $P = I^2R$
  • $P = RV^2$
  • $P = VI$ (correct)

    • What is the unit of the kilowatt-hour (kWh)?

  • Voltage
  • Current
  • Power
  • Energy (correct)

    • Which formula is used to calculate the cost of electricity for an electrical device?

    <p>Cost = Power × Duration × Cost per kWh</p> Signup and view all the answers

    Which formula is used to calculate power in electrical circuits when resistance (R) and current (I) are known?

    <p>$P = I^2R$</p> Signup and view all the answers

    Which of the following is NOT a formula for calculating power in electrical circuits?

    <p>$P = V^2/I$</p> Signup and view all the answers

    What does Ohm's Law state?

    <p>Current is directly proportional to resistance.</p> Signup and view all the answers

    In a series circuit, how are resistors arranged?

    <p>In a single path.</p> Signup and view all the answers

    Which factor does not influence the resistance of a wire?

    <p>Wire color.</p> Signup and view all the answers

    What is power in the context of physics and electrical engineering?

    <p>The rate of work being done.</p> Signup and view all the answers

    How is electrical energy measured?

    <p>In kilowatt-hours.</p> Signup and view all the answers

    What does voltage represent in an electrical circuit?

    <p>Energy difference per unit charge between two points.</p> Signup and view all the answers

    What is the term used to describe the maximum potential difference when no current flows?

    <p>Electromotive force (EMF)</p> Signup and view all the answers

    What causes the drop in voltage when current flows in a battery or cell?

    <p>Internal resistance</p> Signup and view all the answers

    What is the term used to describe the voltage drop within a battery due to its internal resistance?

    <p>Lost volts</p> Signup and view all the answers

    Which type of conductor has a resistance that remains constant as the voltage across it changes?

    <p>Ohmic conductor</p> Signup and view all the answers

    Why is understanding power and energy calculations crucial for designing electrical systems?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of the worked examples and exercises provided in the text?

    <p>All of the above</p> Signup and view all the answers

    What is the relationship between power and energy in electrical systems?

    <p>Power is the rate of energy consumption, and energy is the total amount of power used over time.</p> Signup and view all the answers

    Which of the following is not a practical application of understanding power and energy calculations in electrical systems?

    <p>Determining the optimal voltage and current for a given load</p> Signup and view all the answers

    What characteristic distinguishes Ohmic conductors from Non-Ohmic conductors?

    <p>Resistance remains constant</p> Signup and view all the answers

    What term is used to describe the resistance within a battery or cell that causes a voltage drop when current flows?

    <p>Internal resistance</p> Signup and view all the answers

    What type of graph results from the resistance changes with voltage or current in a conductor?

    <p>Non-linear V-I graph</p> Signup and view all the answers

    What is the real voltage available from a battery reduced by according to the text?

    <p>Internal resistance</p> Signup and view all the answers

    How do Ohm's law and power formulas contribute to electrical system design according to the text?

    <p>Design cost-effective systems</p> Signup and view all the answers

    Which factor influences the resistance of an Ohmic conductor?

    <p>Length of conductor</p> Signup and view all the answers

    Why does understanding power and energy calculations play a crucial role in managing energy consumption?

    <p>To reduce electricity costs</p> Signup and view all the answers

    What concept directly influences circuit design, energy efficiency, and cost management in electrical engineering?

    <p>Power and energy</p> Signup and view all the answers

    Which type of conductor has a resistance that changes with voltage or current?

    <p>Non-Ohmic conductor</p> Signup and view all the answers

    What is the formula for power dissipation through a resistor based on its resistance and current flowing through it?

    <p>P = IR</p> Signup and view all the answers

    Which of the following factors affects the resistance of a wire resulting in higher resistance?

    <p>Higher temperature</p> Signup and view all the answers

    In a parallel circuit, how is the voltage across each resistor related?

    <p>The voltage remains the same across all resistors</p> Signup and view all the answers

    What is the unit of measurement for electrical power consumption used in the text?

    <p>Kilowatt-hours</p> Signup and view all the answers

    How is total resistance calculated in a series circuit?

    <p>$R_T = R_1 + R_2$</p> Signup and view all the answers

    What does electromotive force (emf) represent in an electrical circuit?

    <p>Total energy supplied per unit charge by a battery or cell</p> Signup and view all the answers

    Which formula is used to calculate power consumption of an electrical device given the voltage across it and the current flowing through it?

    <p>$P = IV$</p> Signup and view all the answers

    What is the relationship between power and resistance in an electrical circuit?

    <p>$P = V²/R$</p> Signup and view all the answers

    Which term refers to the capacity to do work in an electrical context?

    <p><em>Energy</em></p> Signup and view all the answers

    What is the formula to calculate power in an electrical circuit when resistance (R) and current (I) are known?

    <p>$P = I^2R$</p> Signup and view all the answers

    In the context of electricity billing, what unit is commonly used to measure energy consumption over time?

    <p>Kilowatt-Hour (kWh)</p> Signup and view all the answers

    Which formula represents power dissipation due to the voltage across a device and its resistance in an electrical circuit?

    <p>$P = RV^2$</p> Signup and view all the answers

    What does the formula $P = VI$ represent in electrical circuits?

    <p>Power dissipation due to resistance</p> Signup and view all the answers

    If the resistance in an electrical device remains constant but the voltage across it changes, which formula would be used to calculate power dissipation?

    <p>$P = RV^2$</p> Signup and view all the answers

    Which formula should be utilized to determine the cost of electricity for an electrical device based on power consumption, duration of usage, and cost per kilowatt-hour?

    <p>$\text{Cost} = \text{Power Consumption} \times \text{Duration} \times \text{Cost per kWh}$</p> Signup and view all the answers

    When calculating power dissipation due to resistance in a device, which formula should be used?

    <p>$P = I^2R$</p> Signup and view all the answers

    What is the term used for a unit of energy equal to the amount of energy used by a load of one kilowatt over one hour?

    <p>$\text{kWh}$</p> Signup and view all the answers

    If you know the current flowing through an electrical device and its resistance, which formula would you use to calculate power dissipation?

    <p>$P = I^2R$</p> Signup and view all the answers

    When both the voltage across a device and its resistance are known, which formula should be used to calculate power dissipation?

    <p>$P = RV^2$</p> Signup and view all the answers

    What is the formula used to calculate power dissipation in an electrical device based on the voltage across the device and the resistance?

    <p>$P = 2RV^2$</p> Signup and view all the answers

    Which formula should be used to calculate power in an electrical circuit when the voltage (V) and current (I) are known?

    <p>$P = VI$</p> Signup and view all the answers

    What is the unit commonly used to measure energy consumption over time in the context of electricity billing?

    <p>Kilowatt-hour (kWh)</p> Signup and view all the answers

    In an electrical circuit, if the resistance (R) and current (I) are known, which formula calculates power dissipation through resistance?

    <p>$P = I^2R$</p> Signup and view all the answers

    What is the definition of power in terms of work done and time interval?

    <p>Power is the rate at which work is done or energy is transferred over time</p> Signup and view all the answers

    When calculating power in electrical circuits, which factor influences power dissipation due to resistance?

    <p>Resistance in the device</p> Signup and view all the answers

    In Ohm's Law, what does the formula $P = 2RV^2$ represent?

    <p>$P$ as a function of both resistance ($R$) and voltage ($V$)</p> Signup and view all the answers

    What characteristic distinguishes Ohmic conductors from Non-Ohmic conductors based on electrical properties?

    <p>Constant resistance with changing voltage or current</p> Signup and view all the answers

    When calculating the cost of electricity for an electrical device, which values are multiplied together?

    <p><em>Power consumption</em> and <em>cost per kilowatt-hour</em></p> Signup and view all the answers

    What is the standard unit for billing electricity usage by energy providers?

    <p>Kilowatt-hour (kWh)</p> Signup and view all the answers

    What determines the total energy consumed by various electrical devices and the efficiency of electrical systems?

    <p>Power and energy calculations</p> Signup and view all the answers

    Which factor contributes to higher resistance in a wire?

    <p>Higher temperature</p> Signup and view all the answers

    What concept directly influences power consumption in electrical circuits?

    <p>Total resistance</p> Signup and view all the answers

    Which formula represents power dissipation through a resistor based on its resistance and the current flowing through it?

    <p>$P = I^2R$</p> Signup and view all the answers

    In which type of conductor does the resistance remain constant as the voltage across it changes?

    <p>Ohmic conductor</p> Signup and view all the answers

    What is the relationship between power, voltage, current, and resistance in electrical circuits?

    <p>Directly proportional</p> Signup and view all the answers

    How is the total resistance calculated in a parallel circuit?

    <p>$R_T = 1/(1/R_1 + 1/R_2 + ...)$</p> Signup and view all the answers

    What does the potential difference represent in an electrical circuit?

    <p>Energy per unit charge</p> Signup and view all the answers

    What distinguishes Ohmic conductors from Non-Ohmic conductors?

    <p>'V = IR' formula applies to both</p> Signup and view all the answers

    'P = V^2/R' is used to calculate what aspect of an electrical circuit?

    <p>$P$ dissipation based on voltage and resistance</p> Signup and view all the answers

    What term is used to describe the maximum potential difference when no current flows in an electrical circuit?

    <p>Electromotive force</p> Signup and view all the answers

    Which of the following factors does NOT influence the resistance of a wire in an electrical circuit?

    <p>Voltage applied across the wire</p> Signup and view all the answers

    Which formula should be used to calculate the cost of electricity for an electrical device based on its power consumption, duration of usage, and cost per kilowatt-hour?

    <p>$ ext{Cost} = P imes ext{Duration} imes ext{Cost per kWh}$</p> Signup and view all the answers

    What term is used to describe the voltage drop within a battery due to its internal resistance?

    <p>Lost volts</p> Signup and view all the answers

    Which type of conductor has a resistance that remains constant as the voltage across it changes, resulting in a linear V-I graph?

    <p>Ohmic conductor</p> Signup and view all the answers

    Which formula should be used to calculate power dissipation in an electrical device when both the voltage across it and its resistance are known?

    <p>$P = V^2/R$</p> Signup and view all the answers

    What is the purpose of the worked examples and exercises provided in the text?

    <p>To test the student's understanding of electrical principles and their applications</p> Signup and view all the answers

    Which of the following is NOT a practical application of understanding power and energy calculations in electrical systems?

    <p>Determining the total resistance in series and parallel circuits</p> Signup and view all the answers

    What is the relationship between power and energy in electrical systems according to the text?

    <p>Power is the rate of energy consumption</p> Signup and view all the answers

    Which law relates the current, voltage, and resistance in an electrical circuit?

    <p>Ohm's Law</p> Signup and view all the answers

    In a parallel circuit, how is the voltage distributed across the resistors?

    <p>The voltage is constant across all the resistors.</p> Signup and view all the answers

    Which formula is used to calculate the power dissipation in a resistor based on the voltage across it and its resistance?

    <p>$P = V^2/R$</p> Signup and view all the answers

    What is the unit commonly used to measure energy consumption in electrical systems?

    <p>Kilowatt-hours (kWh)</p> Signup and view all the answers

    Which of the following factors does NOT influence the resistance of a wire conductor?

    <p>Color of the wire</p> Signup and view all the answers

    Which type of conductor has a resistance that remains constant as the voltage across it changes?

    <p>Ohmic conductor</p> Signup and view all the answers

    Which formula represents the relationship between power, voltage, and current in an electrical circuit?

    <p>$P = VI$</p> Signup and view all the answers

    What is the term used to describe the maximum potential difference when no current flows in an electrical circuit?

    <p>Electromotive force (emf)</p> Signup and view all the answers

    Which formula should be used to calculate the cost of electricity for an electrical device based on its power consumption, duration of usage, and cost per kilowatt-hour?

    <p>$ ext{Cost} = ext{Power} imes ext{Time} imes ext{Cost per kWh}$</p> Signup and view all the answers

    What is the purpose of the worked examples and exercises provided in the text?

    <p>To demonstrate the application of the formulas and principles in real-world scenarios.</p> Signup and view all the answers

    If an electrical device has a power rating of 1.2 kW and operates for 5 hours at a cost of $0.15 per kWh, what is the total cost of electricity consumed?

    <p>$0.90</p> Signup and view all the answers

    A resistor dissipates 100 W of power when a current of 2 A flows through it. What is the resistance of the resistor?

    <p>50 Ω</p> Signup and view all the answers

    In a series circuit with three resistors of 10 Ω, 20 Ω, and 30 Ω, what is the total resistance?

    <p>60 Ω</p> Signup and view all the answers

    If a battery has an electromotive force (emf) of 12 V and an internal resistance of 2 Ω, what is the terminal voltage when a current of 3 A flows through the battery?

    <p>8 V</p> Signup and view all the answers

    A non-ohmic conductor exhibits a resistance that varies with the applied voltage or current. What type of graph would represent the voltage-current relationship for a non-ohmic conductor?

    <p>An exponential curve</p> Signup and view all the answers

    In a parallel circuit with three resistors of 10 Ω, 20 Ω, and 30 Ω, what is the equivalent resistance?

    <p>6.67 Ω</p> Signup and view all the answers

    If a resistor has a resistance of 100 Ω and a voltage of 120 V is applied across it, what is the power dissipated by the resistor?

    <p>144 W</p> Signup and view all the answers

    A battery has an electromotive force (emf) of 12 V and an internal resistance of 1 Ω. If a load of 4 Ω is connected to the battery, what is the current flowing through the circuit?

    <p>2.5 A</p> Signup and view all the answers

    A power plant generates electricity at a rate of 500 MW. If the cost of generating electricity is $0.10 per kWh, what is the cost of generating electricity for 24 hours?

    <p>$1,500,000</p> Signup and view all the answers

    In a DC circuit, a resistor has a current of 3 A flowing through it, and the voltage drop across the resistor is 12 V. What is the power dissipated by the resistor?

    <p>36 W</p> Signup and view all the answers

    If a battery has an internal resistance of 2 and is supplying a current of 3 A, what is the voltage drop within the battery due to its internal resistance?

    <p>$6 V$</p> Signup and view all the answers

    If an appliance has a power rating of 1200 W and operates for 5 hours, what is the energy consumed in kilowatt-hours (kWh)?

    <p>6 kWh</p> Signup and view all the answers

    In a series circuit with three resistors of 3 , 6 , and 9 , what is the total resistance?

    <p>18</p> Signup and view all the answers

    If an electrical device has a resistance of 10 and is connected to a 120 V source, what is the power dissipated by the device?

    <p>120 W</p> Signup and view all the answers

    If the cost of electricity is $0.15 per kWh and an appliance operates for 8 hours with a power rating of 800 W, what is the cost of electricity for that appliance?

    <p>$0.96</p> Signup and view all the answers

    In a parallel circuit with three resistors of 3 , 6 , and 9 , what is the total resistance?

    <p>1.5</p> Signup and view all the answers

    If a Non-Ohmic conductor has a resistance that decreases as the voltage across it increases, what type of graph would represent its V-I characteristic?

    <p>A hyperbolic graph</p> Signup and view all the answers

    What is the term used to describe the maximum potential difference when no current flows in an electrical circuit?

    <p>Electromotive force (EMF)</p> Signup and view all the answers

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