Standard Science Primary 4 Energy

Telephone wires are usually hung loosely between poles during a hot day. This is to ensure that they __________.

A can expand further during the day
B do not snap when they contract on a cold night
C look better when they sag
D conduct electricity better
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Worked Solution

Step 1: Materials lose heat and contract (decrease in length) when they cool down. Step [2-9]: On a cold night, wires will contract. Step [2-9]: If hung tightly, the contraction would cause them to snap.

Correct answer: do not snap when they contract on a cold night

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