QUESTION 4 Throughout this term you use copper leads (wires) to connect differen

Question

QUESTION 4 Throughout this term you use copper leads (wires) to connect different devices and multimeters to assemble various circuits. Calculate the resistance in Ohms of a typical lead, which would have a length of 46.7 cm and a diameter of 1.93 mm QUESTION 5 Standard resistors come in values from 1 Ohm to just under 10 million Ohms (M ), but many projects use resistors between 100 and 1 M . Calculate the resistivity (SI units) of the material used to make a 300 Ohm resistor which has a length of 0.59 cm and a diameter of 1.31 mm

Explanation / Answer

Question 4 -

Resistivity of copper, k = 17.5 x 10^-9 ohm-m

cross-sectional area A = pi*r^2 = 3.141*(1.93/2)^2*10^-6 m^2 = 2.925 x 10^-6 m^2

length L = 46.7 cm = 0.467 m

Resistance R = k*L/A = (17.5 x 10^-9*0.467) / (2.925 x 10^-6) = 2.79 x 10^-3 ohm = 2.79 milli ohm.

Question 5 -

cross-sectional area A = pi*r^2 = 3.141*(1.31/2)^2*10^-6 m^2 = 1.347 x 10^-6 m^2

length L = 0.59 cm = 0.0059 m

Resistance R = k*L/A

=> 300 = k*0.0059 / (1.347 x 10^-6)

=> k = (300 x 1.347 x 10^-6) / 0.0059 = 6.85 x 10^-2 ohm-meter.

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