A electrician finds that a 0.7 m length of a certain type of wire has a resistan
ID: 1592289 • Letter: A
Question
A electrician finds that a 0.7 m length of a certain type of wire has a resistance of 0.15 ?. What is the total resistance of the 151 m of this wire he plans to use? Answer in units of ?.
The current in a resistor decreases by 2.03 A when the voltage applied across the resistor decreases from 14.5 V to 4.19 V. Find the resistance of the resistor. Answer in units of ?.
A resistor is made from a hollow cylinder of length l, inner radius a, and outer radius b. The region a < r < b is filled with material of resistivity p. What is the resistance of this component?
Explanation / Answer
resistance R = rho*L/A
R2/R1 = L2/L1
R2/0.15 = 151/.7
R2 = 32.4 ohms
++++++++++++++++++++++
from ohms law
V = I*R
V1/v2 = I1/I2
I1 - I2 = 2.03 => I2 = I1-2.03
I2 = 2.03+I1
V1 /V2 = I1/(I1-2.03)
14.5/4.19 = I1/(I1-2.03)
I1 = 2.85 A
R = V1/R1 = 14.5/2.85 = 5.09 OHMS <<----------ANSWER
++++++
resistance = rho*L/(pi*(b^2-a^2))
option 5
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