Hi to all,
common glass tube fuses like 3AG and 20x5mm types are made with a variety of wires inside - mostly it is tin plated copper for fast acting " F " types and either pure tin or thickly plated tin over copper for the slow or "T" types.
Tin has a much lower melting temp than copper, so the wire can be thicker for a given rating and this gives it more thermal inertia needed for "slo-blo" action.
But what sort of wire is used in low current fuses with ratings under 1 amp ??
Some 3AG, 250mA "F" fuses I have here use a single strand of silvery coloured wire with the following characteristics:
Cold resistance = 2.9 ohms
Resistance at 250mA = 5.8 ohms
Resistance when red hot = 10 ohms
Wire diameter = 0.04 mm ( 1.6 thou )
Resistance computes as 7.7 times that of pure copper.
Wire is non magnetic plus it flames at the point of opening.
Wire is soldered to the end caps.
..... Phil