find the resistance of 134m of No.20 copper wire at 20 degrees C (p=1.72x10^-6Ohom cm , A= 2.07x10^-2 cm ^2)
13400 cm (1.72*10^-6) ohm cm /2.07*10^-2 cm^2
= [(1.34)(1.72)/(2.07)] * 10^(4-6+2)
= 1.11 Ohms
To find the resistance of a copper wire, you can use the formula:
R = ρ * (L / A)
where:
R is the resistance
ρ (rho) is the resistivity of the material
L is the length of the wire
A is the cross-sectional area of the wire
In this case, we are given the resistivity (ρ = 1.72x10^-6 Ohm cm), the length of the wire (L = 134 m), and the cross-sectional area (A = 2.07x10^-2 cm^2).
Before proceeding, let's convert the units to be consistent. Convert the length from meters to centimeters by multiplying it by 100:
L = 134 m * 100 cm/m = 13400 cm
Now we can substitute the given values into the formula:
R = (1.72x10^-6 Ohm cm) * (13400 cm) / (2.07x10^-2 cm^2)
To calculate this expression, we can use scientific notation multiplication and division rules.
Multiply the numerator: (1.72 * 13400) = 23008
Divide the numerator by the denominator: 23008 / (2.07 * 10^-2) = 1.11 * 10^6 Ohms
So, the resistance of the No.20 copper wire with a length of 134m at 20 degrees C is approximately 1.11 * 10^6 Ohms.