Two cylindrical metal wires of length L=2.00 m and radius r=0.200 mm each are at

Question

Two cylindrical metal wires of length L=2.00 m and radius r=0.200 mm each are attached to each other as shown in figure. The first wire is made of metal with the resistivity rho_1=1.69 times 10^8 ohm.m and the second one - of metal with the resistivity rho_2=2.75 times 10^-8 Ohm.m. A potential difference V=300 mV is applied to the far ends of wires. Calculate the resistance R_1 of the 1^st wire. Calculate the resistance R_2 of the 2^nd wire. What is the current i through the wires? What is the total power P dissipated in wires? What is the magnitude of the current density J_1 through the 1^st wire? What is the magnitude of the current density J_2 through the 2^nd wire? Assume that the carrier charge density (ne) in the 1^st wire is the three times that of the 2^nd wire, (ne)_1=3.00 times(ne)_2, and the left hand side of the arrangement is at higher potential. Calculate the magnitude of the drift velocity v_d2 of electrons in 2^nd wire if its value in the 1^st wire is v_d1=2.50 times 10^-6 m/s. Indicate on the figure directions of the current i and the drift velocities v_d1 and v_d2.

Explanation / Answer

a)
A = pi*r^2
= pi*(0.2*10^-3)^2
= 1.26*10^-7 m^2

R1 = rho1*L/A
R1 = 1.69*10^-8* (2) / (1.26*10^-7)
=0.268 ohm

b)
R2 = rho1*L/A
R2 = 2.75*10^-8* (2) / (1.26*10^-7)
=0.436 ohm

c)
i = V/Rnet
= V/(R1+R2)
= 0.3 V / (0.268+0.436)
=0.426 A

d)
P= i^2*Rnet
= (0.426)^2 * (0.268+0.436)
= 0.128 W

only 4 parts at a time please

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