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A straight wire of length L carries a steady current I. Express the total momentum of all the conduction electrons in the wire (electron mass mₑ, electron charge e).

1. mₑ*I*L/e
2. mₑ*e/(I*L)
3. I/(mₑ*e*L)
4. mₑ*L/(I*e)

Correct answer: mₑ*I*L/e

Solution

Total momentum N*mₑ*v_d simplifies using I = n A e v_d to mₑ I L / e.

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