Question

A rectangular block of copper has sides of length 11 cm, 30 cm, and 45 cm. If the block is connected to a 4.9 V source across two of its opposite faces, find the following.

(a) What is the maximum current the block can carry? [Answer must be in A]

(b) What is the minimum current the block can carry? [Answer must be in A]

I've seen this problem in multiple sites in Chegg, but got different answers with all of them. Can someone help me out to solve this but in a way that I can do it too by using my calculator in case that numbers changes?

Answer 1

R = rho L / A

where rh0 = resistivity of copper = 1.72 x 10^-8 ohm m

(A) for maximum current , R will be smallest possible

{ I = V / R }

and for smallest R, L will be smallest and A will be greatest.

R = (1.72 x 10^-8) ( 0.11) / (0.30 x 0.45)

R = 1.40x 10^-8 ohm

I = V /R = (4.9) / (1.40 x 10^-8) = 3.50 x 10^8 A .....Ans

(B) for minimum current.

R will be greatest.

R = (1.72 x 10^-8) (0.45) / (0.11 x 0.30)

R = 23.45 x10^-8 ohm

I = (4.9) / (23.45 x 10^-8)

I = 0.209 x 10^8 A