Question

37. There are two copper wires of same cross sectional area and they carry
same current. If their lengths are in the ratio 1: 2, then calculate the
ratio of drift-velocity in them.
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Answer 1

Answer ⇒ 1 : 1

Explanation ⇒ Using the formula of the drift velocity,

i = venA

∴ v = i/enA

Now, we can see that drifit veloicty is not affected by the length of the conductor. It can change with change in Area of cross-section, which is same.

∴ Drift velocity is equal in both case.

Hence, Ratio is 1.

Hope it helps.

Answer 2

answer : 1 : 1

drift velocity is given by, $v_d=\frac{i}{neA}$

where i is the current passing through wire, n is the number of electrons per unit volume and A is cross sectional area of wire.

here it is clear that

• drift velocity doesn't depend on length of wire.

in question, both copper wires has same cross sectional area, carrying same current.

so, drift velocity of first copper wire = drift velocity of 2nd copper wire.

or, ratio of drift velocity in them = 1 : 1