Acurrent of 72.4 ma exists in a metal wire. (a) how many electrons flow past a given cross section of the wire in 10.5 min? electrons (b) in what direction do the electrons travel with respect to the current? the magnitude is zero. opposite direction same direction

2.85*10^20 electron, electron travel in the opposite  direction  to the current

Explanation:

By definition, a current of 72.4 mA means that 72.4 * 10^(-3) Coulomb of charge passes a given cross section in a second.

So in 10.5 minutes (630 seconds) = 72.4*10^(-3) * 630 Coulomb passes.

number of electron = \frac{72.4*10^{-3}*630}{1.6 10^(-19) C}

                               = 2.85*10^20 electron

where 1.6 10^(-19) C is charge on electron

electron travel in the opposite  direction  to the current due to opposite charge on each other.

hey , the answer is c

fgravity=10x10=100n case 1

fgravity=30x20=600n case 2

6 times more