# What is the current in an aluminum wire connected to a 3.5V current source?

**What is the current in an aluminum wire connected to a 3.5V current source? Wire length 50m, cross-sectional area 2mm square (aluminum resistivity 0.028 Ohm * mm ^ 2 / m)**

U = 3.5 V.

L = 50 m.

S = 2 mm2.

ρ = 0.028 Ohm * mm2 / m.

I -?

According to Ohm’s law for a section of a circuit, the current I is directly proportional to the voltage at its ends U and inversely proportional to its resistance R: I = U / R.

The resistance R of a homogeneous cylindrical conductor is expressed by the formula:

R = ρ * L / S, where ρ is the resistivity of the conductor, L is the length of the conductor, S is the cross-sectional area.

We find the current strength by the formula: I = U * S / ρ * L.

I = 3.5 V * 2 mm2 / 0.028 Ohm * mm2 / m * 50 m = 5 A.

Answer: in the conductor, the current strength is I = 5 A.