Gr 11 Physical Sciences: Ch 9.2 Power and energy
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Questions and Answers

What is the unit of measurement for power?

  • Joule (J)
  • Ampere (A)
  • Volt (V)
  • Watt (W) (correct)

    • What is the formula for calculating power in an electrical circuit?

  • P = V · I^2
  • P = I / V
  • P = I · V (correct)
  • P = V / I

    • What is power directly proportional to?

  • The square root of the current and voltage
  • The current and voltage (correct)
  • The energy and time
  • The resistance and time

    • What is the purpose of using Ohm's Law to derive additional power equations?

    <p>To provide flexibility in calculating power depending on which quantities are known</p> Signup and view all the answers

    What is the formula for power when the voltage across the circuit element and its resistance are known?

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

    What is the formula for power when the current and resistance in the circuit are known?

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

    What is the rate at which electrical energy is converted in an electric circuit?

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

    What is the definition of power?

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

    What is the unit of power in the formula E = P ⋅ t?

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

    What is the energy consumed by a device with a power rating of 1 kilowatt running for one hour?

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

    To convert power from watts to kilowatts, you should:

    <p>Divide by 1000</p> Signup and view all the answers

    What is the formula to calculate the total energy transferred?

    <p>E = P ⋅ t</p> Signup and view all the answers

    What is the purpose of understanding the principles of electrical power and energy?

    <p>To design electrical circuits for efficient use of energy</p> Signup and view all the answers

    What is the correct order to find the cost of running an appliance?

    <ol> <li>Determine the power rating, 2. Multiply by time, 3. Multiply by cost per kWh</li> </ol> Signup and view all the answers

    What is the unit of electrical energy?

    <p>Joules (J)</p> Signup and view all the answers

    Why is it necessary to multiply the power by the time?

    <p>To calculate the total amount of energy transferred</p> Signup and view all the answers

    What is the total energy consumed by an electrical device equal to?

    <p>The power rating of the device multiplied by the time it is operated.</p> Signup and view all the answers

    Why is it necessary to convert time from minutes or seconds to hours for energy consumption calculations?

    <p>To make the units consistent with kilowatt-hours.</p> Signup and view all the answers

    What is the purpose of calculating the total energy consumption in kilowatt-hours?

    <p>To calculate the cost of electricity.</p> Signup and view all the answers

    What is the cost of running an appliance dependent on?

    <p>The power rating of the appliance, the time it is used, and the cost per kilowatt-hour.</p> Signup and view all the answers

    What is the benefit of understanding the principles of electrical power and energy?

    <p>It helps in calculating the consumption and costs, and also aids in designing and managing electrical circuits effectively.</p> Signup and view all the answers

    How is the cost of electricity calculated?

    <p>By multiplying the power rating of the appliance by the time it is used, and then by the cost per kilowatt-hour.</p> Signup and view all the answers

    What is the unit of measurement for electrical energy in household and commercial contexts?

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

    What is the formula for calculating the total energy transferred in terms of power and time?

    <p>E = P × t</p> Signup and view all the answers

    What is the purpose of a battery in an electric circuit?

    <p>To convert chemical potential energy into electrical energy</p> Signup and view all the answers

    Which of the following is true about the relationship between power and current in an electric circuit?

    <p>Power is directly proportional to the square of the current</p> Signup and view all the answers

    What happens to the power dissipated or consumed by a circuit if the voltage across the circuit elements increases?

    <p>The power increases</p> Signup and view all the answers

    Which of the following formulas is useful when the current and resistance in the circuit are known, but the voltage is not?

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

    What is the effect of doubling the voltage across a circuit element on the power consumed by the circuit?

    <p>The power increases by a factor of 4</p> Signup and view all the answers

    Which of the following statements is true about electrical power?

    <p>Electrical power is a measure of the rate at which work is done</p> Signup and view all the answers

    What happens to the power dissipated or consumed by a circuit if the resistance in the circuit increases?

    <p>The power increases</p> Signup and view all the answers

    Which of the following formulas is useful when the voltage across the circuit element and its resistance are known, but the current is not?

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

    What is the primary function of a battery in an electric circuit?

    <p>To convert chemical potential energy into electrical energy</p> Signup and view all the answers

    Which of the following statements about power is true?

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

    What is the effect of increasing the current flowing through a circuit on the power consumed by the circuit?

    <p>The power increases</p> Signup and view all the answers

    Which of the following formulas is used to calculate power when the voltage and current are known?

    <p>P = I × V</p> Signup and view all the answers

    What is the effect of increasing the resistance in a circuit on the power consumed by the circuit?

    <p>The power decreases</p> Signup and view all the answers

    What is the purpose of deriving alternative formulas for power?

    <p>To make the calculation of power more flexible</p> Signup and view all the answers

    What is the relationship between power and voltage in an electric circuit?

    <p>Power is directly proportional to voltage</p> Signup and view all the answers

    What is the unit of power in an electric circuit?

    <p>Joules per second</p> Signup and view all the answers

    What is the significance of the formula E = P ⋅ t in the context of electrical energy?

    <p>It is used to calculate the total energy consumed by an electrical device.</p> Signup and view all the answers

    What is the primary motivation for converting power from watts to kilowatts in household and commercial contexts?

    <p>To make the energy consumption more relatable to everyday usage.</p> Signup and view all the answers

    What is the key factor that determines the cost of electricity?

    <p>The cost per kilowatt-hour charged by the electricity provider.</p> Signup and view all the answers

    What is the implication of the equation 1 kWh = 1 kW × 1 hour?

    <p>It represents the energy consumed by a device with a power rating of 1 kilowatt running for one hour.</p> Signup and view all the answers

    What is the benefit of understanding the principles of electrical power and energy in designing and managing electrical circuits?

    <p>It aids in the efficient use of energy.</p> Signup and view all the answers

    What is the correct sequence of steps to calculate the cost of running an electrical appliance?

    <p>Determine the power rating, multiply by time, and multiply by cost per kWh.</p> Signup and view all the answers

    What is the significance of the unit kilowatt-hours in the context of electrical energy consumption?

    <p>It is a unit of energy.</p> Signup and view all the answers

    What is the relationship between the power rating of an electrical appliance and its energy consumption?

    <p>The power rating is directly proportional to the energy consumption.</p> Signup and view all the answers

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