A 2.0-m length of wire is made by welding the end of a 120-cm-long silver wire to the end of an 80-cm-long copper wire. Each piece of wire is 0.60 mm in diameter. The wire is at room temperature, so the resistivities are as given in Table 25.1. A potential difference of 9.0 V is maintained between the ends of the 2.0-m composite wire. What is (a) the current in the copper section; (b) the current in the silver section: (c) the magnitude of E → in the copper; (d) the magnitude of E → in the silver; (e) the potential difference between the ends of the silver section of wire?
A 2.0-m length of wire is made by welding the end of a 120-cm-long silver wire to the end of an 80-cm-long copper wire. Each piece of wire is 0.60 mm in diameter. The wire is at room temperature, so the resistivities are as given in Table 25.1. A potential difference of 9.0 V is maintained between the ends of the 2.0-m composite wire. What is (a) the current in the copper section; (b) the current in the silver section: (c) the magnitude of E → in the copper; (d) the magnitude of E → in the silver; (e) the potential difference between the ends of the silver section of wire?
A 2.0-m length of wire is made by welding the end of a 120-cm-long silver wire to the end of an 80-cm-long copper wire. Each piece of wire is 0.60 mm in diameter. The wire is at room temperature, so the resistivities are as given in Table 25.1. A potential difference of 9.0 V is maintained between the ends of the 2.0-m composite wire. What is (a) the current in the copper section; (b) the current in the silver section: (c) the magnitude of
E
→
in the copper; (d) the magnitude of
E
→
in the silver; (e) the potential difference between the ends of the silver section of wire?
Most of the resistance of the human body comes from the skin, as the interior of the body contains aqueous solutions that are good electrical conductors. For dry skin, the resistance between a person’s hands is typically 510 kiloohm. The skin is on average about 2.00 mm thick. We can model the body between the hands as a cylinder 1.60 m long and 12.0 cm in diameter with the skin wrapped around it.
What is the resistivity of the skin?
Wire C and wire D are made from different materials and have length Lc = Lp = 2.4 m. The resistivity and diameter of wire C are 5.0 ×
10-6 Q.m and 1.32 mm, and those of wire D are 1.2 × 106 Q2•m and 0.79 mm. The wires are joined as shown in the figure and a current
of 4.9 A is set up in them. What is the electric potential difference between (a) points 1 and 2 and (b) points 2 and 3? What is the rate at
which energy is dissipated between (c) points 1 and 2 and (d) points 2 and 3?
C
·Lc
(a) Number i 4.3e-5
Units
V
(b) Number
2.9E-5
Units
V
(c) Number i 2.1e-4
Units
W
2
(d) Number i
1.4e-4
Units
W
D
-LD
3
A gold wire 2 mm in diameter and 100 m long is heated to 300°C.
Note: p. = 2.44 x 10 -8 Q-m @ 20° C, a = 3.4 x 10 3 / °C @ 20° C
%3D
%3D
What is the resistivity of the gold wire at 300°C?
O 4.76 x 10-8Q-m
O 2.44 x 1080-m
O 2.32 x 10-8Q-m
O 4.93 x 108 2-m
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