The distance between two electricity transmission pylons is 100 m. A utility company hangs a power cable of length 104 m between them so that it hangs with some slack.
Why does the engineer use a cable that is longer than the straight-line distance between the pylons?
to allow for the thermal contraction of the cable in cold weather
to reduce the electrical resistance of the cable
to ensure the cable remains taut during hot summer days
to decrease the magnetic field strength beneath the power lines
96 exam-style questions on CIE IGCSE Physics 2.2.1 Thermal expansion of solids, liquids and gases. Each one has a worked solution and a mark scheme showing where the marks go.