Answer to Question 2

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  Work out the radius in metres: 

r  = 0.25 10-3

Now work out the area: 

A = pr2 = p (0.25 10-3)2p 6.25 10-8 m2 = 1.96 10-7 m2

Now work out R: R = rl/A .

10 = (47 10-8 Wm l) 1.96 10-7 m

l = 10 1.96 10-7 m2 47 10-84.17 m