electricity question
I have provided the working out and correct answers to i and ii. However for iii) , looking at the mark scheme, only P=I^2 R works. Why does P = V^2 / R not work which is 400^2/0.052?
Because the value of V you have used is not the pd across the cable. It's the potential at one end. The input voltage.
V2/R will work if you use the correct value of V, which is the voltage drop along the cable. Not the input voltage given.
The other formula works because I is the current in the cable and R is its resistance.
V2/R will work if you use the correct value of V, which is the voltage drop along the cable. Not the input voltage given.
The other formula works because I is the current in the cable and R is its resistance.
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