I need help with my homework. I dont understand how to start theproblem. (a) A w

Question

I need help with my homework. I dont understand how to start theproblem.

(a) A wire of 10.0m length and a square (1.0mm x 1.0mm) crosssection is made of a material with a
resistivity of 5.0 x 108W·m. What is its resistance?(b) If a potential difference of 1.00V is maintained
between the ends of the wire, at what rate is heat generated in thewire (i.e. power consumption)? (c)
Three of these wires (identical) are placed side-by-side (inparallel). What is the new power consumed
assuming the same power supply is attached? (d) Five of the wiresare now attached end-to-end (series).
What is the new power consumed?

Explanation / Answer

Length L = 10 m Area A = 1 mm ^ 2 = 10 ^ -6 m ^ 2 resistivity = 5 * 10 ^ -8 ohm m Resistance R = L / A                      =0.5 ohm (b). Potential difference V = 1 V Power consumption P = V ^ 2 / R                                   = 2 watt (c). New resistance   R ' = R / 3 = 0.5 /3 So, power consumption P ' = V ^ 2 / R '                                           = 6 watt (d). New resistance R " = 3 R    Sincethey are in series So, power consumption P " = V ^ 2 / R "                                           = 0.66667 watt

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