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    Input voltage: 400kV.
    Current carried: 440A.
    Resistance per Km: 0.058 Ohms.

    The input power to one cable = VI.

    Yet for some reason, the power wasted as heat = I^2 x R.

    According to the formula booklet, P = VI and P = I^2 x R.

    So shouldn't VI = I^2 x R?

    Please could someone help explain this, and explain how I would normally find the power lost as heat in a cable.

    Imagine the cable had no resistance. Then it could carry all the input power to its destination without loss. The power loss occurs because the resistance of the cable imposes a voltage drop proportional to the current carried. So the 'V' you need in P=VI is the voltage drop in the cable. Which is why it's easier to use I^2R. You'll get an answer in Wm^-1
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