68 mA of current flow through the resistor in the diagram. What is the resistanc

Question

68 mA of current flow through the resistor in the diagram. What is the resistance of the resistor? Ohm In what direction does the current flow through the resistor? The current flows through the resistor A copper wire and an aluminum wire of the same length have the same resistance. What is the ratio of the diameter of the copper wire to that of the aluminum wire? Use = 1.67 times 10-8 ohm . m and = 2.65 times 10-8 ohm . m. / = A bird sits on a high-voltage power line with its feet 6.00 cm apart. The wire is made from aluminum, is 2.00 cm in diameter, and carries a current of 190 A. What is the potential difference between the bird's feet? mv

Explanation / Answer

a)

R=v/i

=4.91/68*10^-3

=72.21 ohms

b)

left to right

c)

here

R=rho*l/A

====>

(R1/R2)=(rho1/rho2)*(l1/l2)*(A2/A1)

(R/R)=(rho1/rho2)*(l/l)*(A2/A1)

1=(rho1/rho2)*(d2/d1)^2

d2/d1=sqrt(rho2/rho1)

d_Cu/d_Al=sqrt(rho_Cu/rho_Al)

=sqrt(1.67*10^-8/2.65*10^-8)

d_Cu/d_Al=0.79

D)

d=3cm then r=3/2=1.5 cm

Area A=pi*r^2 =3.14*1.5^2

A=7.065 cm^2

now

V=i*R

=i*(rho*l/A)

=190*(2.65*10^-8*6*10^-2/7.065*10^-4)

=0.43 mA

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