Question

in a series electric circiit comprising a resistor made up of metallic wire the ammeter reads 5A the reading of the ameter decreases to half when the length of the wire increased why????

Answer 1

hey friend,

=) let the resistance of wire of length ' l' be R

we know that.

=). R = pl/A -------------------(1)


so when length is increased suppose length becomes '2l ' then area becomes half A/2

new resistance becomes R'

so =). R' = p(2l)/(A/2)
.
=). R' = 4 (pl/A) -------------------(2)

dividing equation (1) /(2) we get

=) R'/R = 4/1

=) R' = 4R ------------(3)

so from equation 3 we can say that on increasing length of conductor resistance increases ..

as we know that resistance opposes the current flowing so on increasing length resistance increases leading to less current flow through the ammeter so ammeter reading decreases.

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hope it will help u. (^_^)