In Figure ( a ) below, a 10.98 V battery is connected to a resistive strip that
ID: 1429510 • Letter: I
Question
In Figure (a) below, a 10.98 V battery is connected to a resistive strip that consists of three sections with the same cross-sectional areas but different conductivities. Figure (b) gives the electric potential V(x) versus position x along the strip. The horizontal scale is set by xs = 8.24 mm. Section 3 has conductivity 3.031 × 107 (?·m)-1. What is the conductivity of section (a) 1 and (b) 2?
2) A heating element is made by maintaining a potential difference of 77.0 V across the length of a Nichrome wire that has a 3.81 × 10–6 m2 cross section. Nichrome has a resistivity of 5.00 × 10–7 ?·m. (a) If the element dissipates 7620 W, what is its length? (b) If 103 V is used to obtain the same dissipation rate, what should the length be?
Explanation / Answer
2) Power = V^2 / R
7620 W = 77^2 / R
R = 0.778 ohm
and Resistance, R = resistivity x L / area
0.778 = 5 x 10^-7 x L / (3.81 x 10^-6)
L = 5.93 m ........Ans
b) Now resistance is changed.
7620 = 103^2 / R
R = 1.39 ohm
1.39 = 5 x 10^-7 x L / (3.81 x 10^-6)
L = 10.61 m ........Ans
In question 1. Figure is missing .