WAEC - Physics (1992 - No. 43)
Calculate the length of a constantan wire of cross- sectional area 4 π x 10-8m2 and resistivity 1.1 x 10-6 Ω m required to construct a standard resistor of resistance 21 Ω. [Take π = 22/7]
0.42m
2.40 m
6.25 m
183.75 m
590.00 m
คำอธิบาย
R = PL/A => L =
RAP
= 21 x 4π x 1081.1 x 10-6
= 2.40