Math questions (science related)? Please help..Thanks!?

1) A 100-watt incandescent light bulb is left on in a bedroom two days every week for a year. If electricity costs 12¢ per kWh, how much extra does this cost the family this year?

2) The average energy used by an American in a year is 7.5 TOE (ton of oil). What is the average power consumption of an average American family of four in watts?

1 Answer

Relevance
  • 1 month ago
    Favorite Answer

    1) A 100-watt incandescent light bulb is left on in a bedroom two days every week for a year. If electricity costs 12¢ per kWh, how much extra does this cost the family this year?

    cost = 100w * 2day/week * 52wk/yr * 24hr/day * 1kw/1000w * $0.12/kwh

    cost = $29.952/year <––––––

    --------------------------

    2) The average energy used by an American in a year is 7.5 TOE (ton of oil). What is the average power consumption of an average American family of four in watts?

    From wikipedia: https://en.wikipedia.org/wiki/Tonne_of_oil_equival...

    1 TOE = 11.63 megawatt-hours

    7.5 TOE = 11.63 * 7.5 = 87.225 mwh

    Power = 87.225mwh * 1day/24hr * 1 year/365day * 1000kw/1mw

    Power = 9.957 kw 

    4 people

    power = 4 * 9.957

    power = 39.828 kw <––––––

    --------------------------

    Note: Many people incorrectly interchange power and energy, but they are different units.

    Power is watts. Energy is watt-hours.

    Example:  60 watts is the power required to operate a 60 watt light bulb.

    The energy it uses in 10 hours would be 600 watt-hours or .6kwh

Still have questions? Get your answers by asking now.