The rheostat winding is made of a wire 50 m long and a cross-sectional area of 2 mm squared.

The rheostat winding is made of a wire 50 m long and a cross-sectional area of 2 mm squared. Is the current in the winding of the rheostat 3A, is it connected to the network with a voltage of 30V? Determine the resistivity of the wire.

Let us determine what the resistance will be equal to, when from the condition of the task we know that the current strength is 3 amperes, while the voltage is equal to 30 volts:

R = U / I;

R = 30: 3 = 10.

Let us determine what the resistivity of the wire will equal, when from the condition of the task we know that its cross-sectional area is 2 mm2, with a length equal to 50 meters:

p = RS / L;

p = 10 * 2: 50 = 0.4.

Answer: With such initial data, the resistivity will be equal to 0.4 Ohm * mm2 / m.