Nichrome wire, often used for heating elements, has resistivity of 1.0 × 10-6 ω • m at room temperature. what length of no. 30 wire (of diameter 0.250 mm) is needed to wind a resistor that has 50 ohms at room temperature?

Length of wire will be 2.45 m

Explanation:

We have given resistivity of the wire

Diameter d= 0.25 mm

So radius

Area

Resistance of wire = 50 ohm

We know that resistance is given by

So

So length of wire will be 2.45 m

the answer would be   dignified - apex

it has to be b, about 97 percent.