The heating element of a simple heater consists of a 2.1 m long, 0.65 mm diamete
ID: 1498704 • Letter: T
Question
The heating element of a simple heater consists of a 2.1 m long, 0.65 mm diameter nichrome wire. When plugged into a 120 V outlet, the heater draws 7.0 A of current when hot. Part A What is the wire's resistance when it is hot? Part B Use your answer to part A to calculate the resistivity of nichrome in this situation.
I got 17.14 ohms for part A. For part B I solved R= roe*L/A so roe = RA/L and get 2.686 x 10^ -6 or 2.7 to 10^-6 as two sig figs (what told to answer in). I get it as wrong. Could you step by step show me and give me a two sig fig answer. I'm starting to think it is a calculator issue. Although I'm in degrees with my calculator
Explanation / Answer
ower = VI = 120*7 = 840W = (I^2)R
840 = 7^2 * R ==> R = 840/49 = 17.14 ohms
B) R = resistivity*L/A A = pi(0.65*10^-3 / 2 )^2 = 3.31*10^-7 m^2
17.14 * 3.31*10^-7 /2.1 = resistivity
Resistivity = 2.708 *10^ -6 ohm -m
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