On seeing some of the past papers it appears that some easy marks can be gained by remembering basic electrical theory in relation to cables.
The conductors within a cable have a given resistance for a given cross sectional area (csa) depending upon the metal used. Copper is not the only metal since aluminium is also used.
The questions tend to ask if the length if increased or decreased and also if the csa is increased or decreased what value of resistance would be obtained.
Altering the length of the cable is equivalent to resistors in series whereas altering the csa is equivalent to resistors in parallel.
Let us assume I have a cable of a length and csa that gives me 1.2 ohm. (long cable). If I double it's length then I have 2*1.2 ohm or 2.4 ohms. If I half it's length then I have 1.2/2 or 0.6 ohms.
The same cable above is now doubled in csa so this will lower the resistance since we have effectively two resistors in parallel thus for same length the resistance will be 1.2/2 or 0.6 ohms.
So if we double it's length and also double the csa we get (2*1.2)/2 or 1.2 ohm. Notice that the resistance is the same, namely 1.2 ohm. If we half it's length and half it's csa then we have (1.2/2)*2 or once again 1.2 ohm.
If you imagine that the cable is an actual resistor it may be easier to remember when doing the exam.
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