A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9(A) What will be the radius of the wire that will blow off at a current of 1A?
A)0.2 mm
B)0.18 mm
C)0.28 mm
D)0.3 mm

Question

Quizplus · Accepted Answer

The current that a fuse wire can carry is proportional to the cross-sectional area of the wire. Since the area is proportional to the square of the radius, the ratio of the currents is equal to the square of the ratio of the radii. Solving for the new radius: (1/9) = (r_new/0.8)^2, gives r_new = 0.8 * sqrt(1/9) = 0.8 * 1/3 = 0.8/3 = 0.267 mm, which is approximately 0.18 mm.

A Fuse Wire of Circular Cross Section Has a Radius