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5. Power and Efficiency

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In this mini-lecture, we introduce the concepts of power and efficiency. In particular, we consider: (i) the definition of power as the rate of energy per unit time; (ii) the units of power (the Watt); (iii) two examples that highlights the difference between the total amount of energy produced in a system and the rate at which the energy was produced (the power); (iv) the definition of efficiency as the ratio of output to input energy or power; (v) an example involving efficiency; (vi) how systems we have discussed can improve their efficiency; and (vii) energy in the UK and globally.


In this course, Professor Douglas Halliday (Durham University) explores energy. In the first mini-lecture, we discuss the big picture of energy, looking at types of energy, key principles, and units. In the second mini-lecture, we consider changes in energy by looking at examples of various energy exchanges involving kinetic and potential energy, heat, electrical energy, etc. The third mini-lecture introduces the concept of the conservation of energy and works through four related examples. In the fourth mini-lecture, we discuss the concept of work in greater detail and go through a couple of examples. In the fifth mini-lecture, we introduce the concepts of power and efficiency, working through some examples and looking at how to improve the efficiency of a system.


Douglas Halliday is a Professor of Physics at Durham University and a Director at the Durham Energy Institute. His research involves next-generation thin-film photovoltaic (solar) devices. Professor Halliday is also the Director of the Centres for Doctoral Training in Energy and Global Challenges Research as well as the Chair of the European Universities Association Energy and Environment Platform (EUA-EPUE).

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APA style

Halliday, D. (2022, January 14). Energy - Power and Efficiency [Video]. MASSOLIT.

MLA style

Halliday, D. "Energy – Power and Efficiency." MASSOLIT, uploaded by MASSOLIT, 14 Jan 2022,

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