Chapter 9 Multiple choice questions

. Section 9.2 describes the basic processes of generating electricity, and Box 9.1 describes alternating current. The UK domestic electricity supply is rated at 230 volts r.m.s. What does the 'r.m.s.' stand for?

. Nikola Tesla was an important figure in developing early mains electricity supplies. What technology was he a particular pioneer in?

. It is possible to distribute electricity at many different voltages. Long distance transmission is likely to be done at what voltage?

. Section 9.3 describes the development of electric lighting. In 2014 a Nobel Prize in physics was awarded for producing what?

. Section 9.5 describes electric traction and Box 9.8 critical rare elements. Which element is used with cobalt to make strong permanent magnets for motors and generators?

. Section 9.5 describes the expanding uses of electricity including refrigeration. Box 9.10 describes the environmental problems caused by some refrigerants. Which refrigerants have contributed both to global warming and the ozone hole?

. Section 9.6 describes large scale electricity generation. Figure 9.42 in Box 9.11 shows a CCGT generation plant. Its turbine inlet temperature is 1140 degrees Celsius and the low pressure water vapour entering the condenser is at 22 degrees Celsius. What is the Carnot efficiency (the maximum possible efficiency) of a heat engine operating between these two temperatures? (Hint: Remember to convert from degrees Celsius to temperature in kelvins.) Is it:

. Section 9.7 describes electrical transmission and distribution. What is unusual about electricity distribution in Japan?

. Section 9.8 describes balancing supply and demand on the grid. In August 1999 a total eclipse of the sun was visible in the UK. Over three-quarters of an hour the demand dropped by 2.2 GW as people stopped work to look at it and then rapidly rose by 3 GW as they went back to work. What type of power plant might be used to cover the bulk of such a power variation?

. Section 9.9 describes electricity use in a number of different countries. In 2016-17 what proportion of electricity in India was used by agriculture?

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