Question

a) A 4.7 g wire has a density of 4.8 g/cm^3 and a resistivity of 9 × 10^−8 Ω · m . The wire has a resistance of 66 Ω . How long is the wire? Answer in units of m.

b) The wire is made up of atoms with molecular mass 75 g/mol. What is the drift speed of the electrons when there is a voltage drop of 132 V across the wire? Assume there is one conduction electron per atom. The fundamental charge is 1.602 × 10^−19 C. Answer in units of m/s.

Answer 1

R = L / A

where L is length, A is area, and is resistivity.

First, we need to find volume of wire

volume = mass/density

volume = 4.7e-3 / 4800

volume = 9.79e-7 m³

Now, we know that

volume = area * length

Therefore,

area = V/L

Therefore,

R = * L / V/L

R = * L² / V

solve for L, we get

L = 26.796 m

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In second question, what are the valence electrons ?? Let me know...

Anyway, here is how to do this part

Find the current

I = V/R

I = 2 A

Now, find the area

A =  9.79e-7 / 26.796

A = 3.65e-8 m²

now, mass of 1m³ = 4.8e3 Kg

Then find mass of atom by multuiplying 75 g/mol with molecular mass.

Then use v = I/nAe to find the velocity.

where n = number of valence * number of atoms per m³