Problems - Resistivity P17-10. (0) A crow sits on a cm diameter copper (p = 1.67

Question

Problems - Resistivity P17-10. (0) A crow sits on a cm diameter copper (p = 1.67 x 10^-8 ohm m) wire, which carries a current of 70 amps. If the bird?s feet are 11cm apart, find A) the potential difference between the bird?s feet. B) If the bird ate away the wire?s insulation, how much current would flow through the bird, whose resistance is 0.4 M ohm? P17-11s. Find the resistance of a s m long copper wire with cross-sectional area 2 x 10^-5 m^2. Use 1.67 x 10^-8 ohm m for the resistivity of copper. P17-12. (0) If a human being has a resistance of 1.5 M ohm. what length copper wire of cross-sectional area 2 .5 x 10^-5 m^2would be required in order to achieve the same value of resistance? (Use 1.67 x 10^-8 ohm m for the resistivity of copper.) Compare your answer to a common length.

Explanation / Answer

Formula to use is R=pL/A

where R=resistance

p=resistivity

L=Length

A=area

second one

R=pL/A

=1.67*10^-8*3/2*10^-5

=5.01*10^-8/2*10^-5

=2.5*10^-3ohm

R=2.5 mohm

third one

R=pL/A

1.5*10^-3=1.67*10^-8*L/2.5*10^-5

3.75*10^-8=1.67*10^-8*L

L=2.24m

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