KCET · Physics · Current Electricity

Though the electron drift velocity is small and electron charge is very small, a conductor can
carry an appreciably large current because

A electron number density depends on temperature
B electron number density is very large
C relaxation time is small
D drift velocity of electron is very large

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Answer & Solution

Correct Answer

(B) electron number density is very large

Step-by-step Solution

Detailed explanation

(B)
Current I = neAV \( _{d} \)
The large value of \( I \) is because of number density of free electrons in a conductor \( (n) \)
which is of the order \( n=10^{28} \) per \( m^{3} \)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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Though the electron drift velocity is small and electron charge is very small, a conductor cancarry an appreciably large current because

Step-by-step Solution

Though the electron drift velocity is small and electron charge is very small, a conductor can
carry an appreciably large current because