# Physics

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A "Bus" bar is in the form of a slab of copper 2meters long, 1cm wide, and 10 cm thick.
a) What is the resistance of the bar at 0 degrees celcius?
b) What potential difference is needed to push 5000 amps through the bar?

• Physics -

Look up the resistivity of copper. Call it r. For pure copper,
r = 1.67*10^-7 ohm-cm

(a) Multiply "r" by the bar's length (200 cm) and divide by the cross sectional area (10 cm^2), to get the resistance in ohms, R.

(b) V = I * R (volts)

I = 5000 A
Solve for V

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