Question

Always use significant figure rules. Remember that these rules apply to all numbers that are measurements.

Compute the resistance of a 90-cm length of copper wire with a 0.020 -cm2 cross-sectional area. ( = 1.8 x 10-6 ohm-cm)

R = ohms
A 4.0 x 10^-1
B 1.3 x 10^11
C 8.1 x 10^-3
D 2.5 x 10^9

Answer 1

C C C C C C C C C

Step-by-step explanation:

IGHT

Answer 2

I'll assume
`\rho=1.8*10^(-6)` (resistivity of the wire), I'm pretty sure this is the case given that the units you provided go accordingly with those of resistivity.

For a wire with cross-sectional area
`A`, length
`l`, and resistivity
`\rho`, then its resistance
`R` is given by:

`R= (L\rho)/(A)`

So, for your example:

`R= (L\rho)/(A)=((90)(1.8*10^(-6)))/(.02)=.0081=8.1*10^(-3)`

Hence, the answer is C.