Question

The current flowing inside a copper wire of cross-sectional area 0.240cm2 and length 0.99m is 340 A Given that the number of charge carriers per unit volume is 8.49 × 1028 m-3 , Calculate the time taken for the electrons to move from the car battery to the starting motor

Answer 1

Given

Current $I=340 A$

 number of charge carriers per unit volume is $n=8.49 × 10^{28} /m^3$

Charge of an electron is $e=1.60×10^{-19} C$

Area is $A=0.240×10^{-4} m^2$

Length is $d=0.99 m$

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The time taken for the electrons to move from the car battery to the starting motor is

$t=\frac{neAd}{I}$

$=\frac{(8.49×10^{28)} )(1.60×10^{-19})(0.240×10^{-4})(0.99)}{340}$

$=949 s =15.8 min$