P7.2 Power and Efficiency

    Cards (63)

    • One watt represents 1 joule of energy transferred per second.

      True
    • Efficiency is the ratio of useful energy output to total energy input
    • Order the steps to calculate efficiency:
      1️⃣ Identify the total power input
      2️⃣ Identify the useful power output
      3️⃣ Divide the useful power output by the total power input
      4️⃣ Multiply the result by 100%
    • One watt is defined as the energy transferred or work done at a rate of 1 joule per second
    • What does efficiency measure in a system?
      How well energy is converted
    • Calculating efficiency helps determine how much energy is lost or wasted.

      True
    • If a 100 W light bulb transfers 1000 J of energy in 10 seconds, what is its power?
      100 W
    • One watt represents 1 joule of energy transferred per second.

      True
    • What is the formula for power in terms of force and velocity?
      P = F*v
    • What does 1 watt represent in terms of energy transfer?
      1 joule per second
    • To convert watts to kilowatts, divide by 1000
    • How many kilowatts is 2500 watts equivalent to?
      2.5 kW
    • What is the formula for calculating efficiency?
      (Useful output / Total input) × 100%
    • What is the formula for calculating power using energy and time?
      P = E/t
    • A 100 W light bulb that is on for 10 seconds transfers 1000 J of energy
    • Efficiency is expressed as a percentage.

      True
    • What does energy transformation refer to?
      Conversion of energy
    • Burning coal to produce electricity is 100% efficient.
      False
    • How many kilowatts is 2500 watts equivalent to?
      2.5 kW
    • Power (P) is equal to the energy (E) transferred divided by the time
    • If a 100 W light bulb transfers 1000 J of energy in 10 seconds, what is its power output?
      100 W
    • What does efficiency measure in a device?
      Energy conversion
    • If an engine uses 5000 W of power and delivers 3000 W of useful work, what is its efficiency?
      60%
    • Steps to calculate efficiency
      1️⃣ Identify the total power input
      2️⃣ Identify the useful power output
      3️⃣ Divide the useful power output by the total power input
      4️⃣ Multiply the result by 100%
    • What is the typical efficiency of a combustion engine?
      25-35%
    • Match the energy transformation with its typical efficiency:
      Electric motor ↔️ 75-95%
      Solar panel ↔️ 15-20%
      Combustion engine ↔️ 25-35%
    • Energy transformation refers to the conversion of one form of energy into another.
      True
    • Higher efficiency transformations are more desirable because they minimize energy losses and environmental impact
    • Efficiency measures how well a system converts energy into useful work
    • Optimizing the design of a device can involve improving insulation to minimize heat loss
    • Devices with higher efficiency components reduce energy waste and environmental impact.

      True
    • The unit of power is the watt
    • Match the unit of power with its abbreviation and conversion:
      Watt ↔️ W ||| 1 W = 1 joule/second
      Kilowatt ↔️ kW ||| 1 kW = 1000 W
    • How is efficiency expressed?
      As a percentage
    • Understanding power is crucial for designing efficient systems
    • To convert kilowatts to watts, you multiply by 1000.

      True
    • The formula to calculate power using energy and time is P = E/t
    • The unit of power is the watt
    • What is the formula for power in terms of energy and time?
      P = E/t
    • The unit of power is the watt
    See similar decks