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US

5393845

Question | Answer |

What is the equation relating energy transferred, mass, temperature change and specific heat capacity? | Energy = mass x temperature change x specific heat capacity |

How do you work out mass from this equation? | Mass = energy / (temperature change x specific heat capacity) |

How do you work out temperature change from this equation? | Temperature change = energy / (mass x specific heat capacity) |

How do you work out specific heat capacity from this equation? | Specific heat capacity = energy / (mass x temperature change) |

What are the units of energy, mass, temperature change and specific heat capacity? | Joules (J), Kilograms (Kg), Degrees Celsius (C), Joules per kilogram degrees C (J/Kg C) |

A 60kg block of aluminium is heated by 20 degrees. The specific heat capacity of Al is 900. Calculate the energy transfer. | Energy = 60 x 20 x 900 = 1,080,000 J |

What is the equation relating efficiency, total energy\power input and useful energy\power output? | Efficiency = useful energy\power output / total energy\power input (x 100%) |

How do you work out the useful energy\power output from this equation? | Useful energy\power output = efficiency x total energy\power input |

How do you work out the total energy\power input from this equation? | Total energy\power input = useful energy\power output / efficiency |

What are the units for efficiency, total energy\power input and useful energy\power output? | % or decimal, Joules (J) (Energy) or Watts (W) (Power) |

An LED bulb uses 50J of energy and emits 37J of light energy, 1J of sound energy and 12J of heat energy. Calculate the efficiency of the LED bulb. | Efficiency = 37 / 50 (x 100) = 74% |

What is the equation linking energy transferred, power and time? | Energy transferred = power x time |

How do you work out power from this equation? | Power = energy transferred / time |

How do you work out time from this equation? | Time = energy / power |

Name one set of units that can be used for energy transferred, time and power. | Joules (J), Seconds (S) and Watts (W) |

What is the other set of units that can be used for energy transferred, time and power? | Kilowatt-hours (kWh), Hours (Hrs) and Kilowatts (kW) |

Bob leaves his radiator on for three and a half hours. It uses seventeen kilowatts of power every hour. What is the energy transfer whilst the radiator is on? | 17 x 3.5 = 59.5 kW 59.5 x 3.5 = 208.25 kWh |

What is the equation linking speed, frequency and wavelength? | Speed = frequency x wavelength |

How can you work out frequency using this equation? | Frequency = speed / wavelength |

How can you work out wavelength using this equation? | Wavelength = speed / frequency |

What are the units for speed, frequency and wavelength? | Metres per second (m/s), Hertz (Hz) and metres (m) |

A wave has a frequency of 15,000 Hz and a wavelength of 20,000 m. Calculate its speed. | 15,000 x 20,000 = 300,000,000 m/s or 3.0x10^8 m/s |

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