Saturday, April 14, 2012

Voltage/ Charge question!!!?

A hair dryer draws a current of 9.5 A.



(a) How much charge passes through the hair dryer in 3.5 min?



______C



(b) How many electrons does this represent?



______electrons



Voltage/ Charge question!!!?

Actually.....1 Ampere is 1 Coulomb per second



1A=1C/s not the other way around.



So, the amount of charge is given by:



xCoul = yAmp . zsec



Where y = 9.5 and z = 3.5 times 60 sec



so, x = 19950Coulombs



For part b), simply divide this by the charge on one electron



Voltage/ Charge question!!!?

Current is defined as the change in charge per unit time.



1 Coulomb (charge) = 1 ampere/second



3.5 minutes * (60 s/minute) = 210 s



x C = 9.5 ampere/210 seconds



The charge of a single electron is 1.6 * 10^-19C (see second reference below).



Take x from your previous answer and divide it by the charge per electron, and you will have the number of electrons.



So, electrons = x coulombs / (1.6 * 10^-19 coulombs/electron).



Voltage/ Charge question!!!?

a) Q=charge, I=current, t=time



Q=It =9.5*(3.5*60) =1995C



b) Charge of an electron= -1.6*10^-19



No. of electrons=1995/ (1.6*10^-19) = 3.192*10^-16

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