An electrical circuit is assembled, consisting of a current source, a resistor, a voltmeter, an ammeter

An electrical circuit is assembled, consisting of a current source, a resistor, a voltmeter, an ammeter, a key. Voltmeter reading is 3.5V, ammeter 0.35A. Wire cross-sectional area 0.2mm 2, length 4m. Determine what material is the resistor wire made of?

U = 3.5 V.

I = 0.35 A.

S = 0.2 mm2.

l = 4 m.

ρ -?

We express the wire resistance of the resistor R from Ohm’s law for a section of the circuit: R = U / I, where U is the voltage at the ends of the resistor, I is the current in the circuit.

The resistance R of a homogeneous cylindrical conductor is determined by the formula: R = ρ * l / S, where ρ is the resistivity of the material from which the conductor is made, l is the length of the conductor, S is the cross-sectional area.

U / I = ρ * l / S.

ρ = U * S / I * l.

ρ = 3.5 V * 0.2 mm2 / 0.35 A * 4 m = 0.5 Ohm * mm2 / m.

According to the table of specific resistance of substances, we see that the resistor is made of constantan.

Answer: The resistor is made of constantan material.