Electrical Power and Energy Quiz
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Questions and Answers

What is the formula to calculate current if power and voltage are known?

  • I = E ÷ P
  • I = P ÷ E (correct)
  • I = P x E
  • I = E x P

    • How many watts does a 1.5 hp motor approximately consume at 28 volts?

  • 746 watts
  • 1,119 watts (correct)
  • 560 watts
  • 1,120 watts

    • If a resistor dissipates power, what is the direct relationship to current and voltage?

  • Power is proportional to the square of the current and resistance. (correct)
  • Power is constant regardless of current and voltage.
  • Power is independent of resistance.
  • Power is inversely proportional to the voltage and current.

    • What is the total power consumed by a circuit with a voltage of 12 volts and a current of 20 amps?

    <p>240 watts</p> Signup and view all the answers

    What describes energy in the context of power calculations?

    <p>Stored capacity to perform work</p> Signup and view all the answers

    What is the relationship between watts, volts, and amps?

    <p>Watts = volts x amps</p> Signup and view all the answers

    How many joules of energy does 1 watt provide in 1 second?

    <p>1 joule</p> Signup and view all the answers

    How long can 1.5 kilojoules of energy provide 25 watts of power?

    <p>1 minute</p> Signup and view all the answers

    What type of energy is associated with the position or internal state of an object?

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

    What does the principle of conservation of energy state?

    <p>Energy is converted from one form to another.</p> Signup and view all the answers

    In what form is a battery's energy stored?

    <p>Chemical potential energy</p> Signup and view all the answers

    When current flows through resistance, what type of energy conversion occurs?

    <p>Electrical energy to heat energy</p> Signup and view all the answers

    What is the SI unit of energy?

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

    What is the unit of measurement for power?

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

    What does the power rating of an electrical component indicate?

    <p>The rate at which it converts electrical energy</p> Signup and view all the answers

    If a resistor is rated for 3 watts, what is the typical maximum power that should be used?

    <p>3 watts</p> Signup and view all the answers

    How is power dissipated by a resistor related to its size?

    <p>Larger resistors dissipate heat more effectively.</p> Signup and view all the answers

    What is the formula for calculating work?

    <p>Work (W) = Force (F) x Distance (D)</p> Signup and view all the answers

    What is the appropriate power dissipation for a resistor with 6 Volts applied and a current of 100 mA?

    <p>0.6 Watts</p> Signup and view all the answers

    Which unit is commonly used to measure power in electrical systems?

    <p>Watt (W)</p> Signup and view all the answers

    Which of the following statements about resistors and their ratings is correct?

    <p>Typically, actual power used by a resistor is considerably less than its rating.</p> Signup and view all the answers

    What safety factor is typically used when selecting a resistor based on power consumption?

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

    Which of the following correctly describes the relationship between work and power?

    <p>Power is the rate at which work is done.</p> Signup and view all the answers

    If an engine lifts a weight of 400 lbs over a distance of 10 ft, what is the total work done?

    <p>4,000 ft/lbs</p> Signup and view all the answers

    Which of the following represents the potential risk for small resistors under high current?

    <p>They can overheat quickly.</p> Signup and view all the answers

    What happens when voltage is present, but the circuit is open?

    <p>No current flows and no work is done.</p> Signup and view all the answers

    How does horsepower relate to watts?

    <p>1 hp = 746 W</p> Signup and view all the answers

    In the SI metric system, what is the unit of work?

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

    When does work occur in a physical context?

    <p>When a force acts on an object and sets it in motion.</p> Signup and view all the answers

    What are the three ways to increase the dissipation of heat from a resistor?

    <p>Size, airflow, heat sinks</p> Signup and view all the answers

    What is the formula for calculating power using current and resistance?

    <p>P = I²R</p> Signup and view all the answers

    How much power is dissipated when 12 volts are applied to a load drawing 2 amps?

    <p>24 watts</p> Signup and view all the answers

    If a resistor has a resistance of 20 ohms and carries a current of 4 amps, what is the power dissipated?

    <p>320 watts</p> Signup and view all the answers

    What is the current draw of two 100-watt driving lights in a car powered by a 12-volt supply?

    <p>16.66 amps</p> Signup and view all the answers

    What is the maximum power load on a circuit rated for 20 amps at 12 volts?

    <p>200 watts</p> Signup and view all the answers

    Which of the following correctly states Ohm's Law?

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

    What is the relationship between power (P), voltage (E), and current (I)?

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

    Study Notes

    Module 3: Electrical Fundamentals - Topic 3.8: Power

    • Power is defined as the rate at which work is done.
    • The electrical unit of power is the Watt (W).
    • Work is done when a force causes motion. Work is the product of force times distance (W = F x D).
      • Examples include lifting a weight, or moving an object.
      • Units of work are typically foot-pounds (ft/lbs) in the English system and joules (N x m) in the metric system.
      • 1 joule = 1 Newton x 1 metre
    • Energy (kinetic and potential) relates to work.
      • Kinetic energy is associated with motion.
      • Potential energy is associated with position or internal state.
    • A resistor dissipates electrical energy as heat.
    • Power is also the rate of change of electrical energy into another form of energy (such as heat).
    • Power is measured in watts.
    • Power (P) = Voltage (V) x Current (I) or Watts = Volts x Amps.
      • Ohm's law states V=IR (Voltage = Current x Resistance).
      • Combining the 2 equations gives you : P=I^2 * R, or P = V^2 / R
    • The SI unit of energy is the joule. One joule of energy can do one joule of work. One joule of energy could supply one watt of power for one second.
    • Horsepower (hp) is a unit of power. 1 hp equals 746 watts.
    • Components are often rated by maximum power (in watts).
    • A safety factor is typically used in electrical component calculations, and typically is 50%.
    • Heat sinks are used to increase heat dissipation.
    • Size and airflow also contribute to heat dissipation.

    Formula Wheel Notes for Power Calculations

    • The formula wheel shows different equations for calculating electrical power, voltage (V), current (I) and resistance (R).
    • These equations are derived from Ohm's Law and Power Law.
      • Note equations for different forms can be used to calculate one unknown if knowns are given
    • Use the wheel to find the appropriate equation.
    • Example calculations are provided in the slides about how to use the formula wheel.

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    Related Documents

    B - A - 3.8 - Power PDF

    Description

    Test your knowledge on electrical power concepts, including the relationships between current, voltage, and power. This quiz covers key formulas, energy concepts, and practical applications in electrical circuits. Perfect for students studying physics or electrical engineering.

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