Two wires each of radius of cross-section r but of different materials are connected together end to end (in series). If the densities of charge carriers in the two wires are in the ratio 1:4, the drift velocity of electrons in the two wires will be in the ratio
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Solution
If the wires are connected end to end (in series) then current in them will be same.
We know formula of current,
I=neAvd
where, n→ number of free electrons per unit volume e=1.6×10−19C A→ Area of cross-section vd→ Drift velocity
As current and cross-section is same then
n1eAvd1=n2eAvd2
⇒vd1vd2=n2n1=41
Hence, option (c) is correct.
Why this question ?
If two wires are connected in series, then current in them will be same
Key Formula: If electrons are moving with velocity vd,A is area of cross-section and n is the number of free electrons per unit volume then, I=neAvd