Amount of charge flowing through a resistor?

druuuuuuuunnk

Amount of charge flowing through a resistor???

the current through a resistor is 3 mA. What charge will flow through it in 200 seconds?

if the resistor has a resistance of 2.0 kΩ what will be the power dissipated in it?

for the first one, i have no idea. i cant seem to find any formula that is relavent to this so im guess the answer is simple but im missing a vital piece of information that would link the dots.

for the second one i was thinking the power disippated in the resistor would be the same as the resistance, becuase the resistance is stopping anything above 2.0 V to enter the resistor?

any help is appriated, this is for my exam tomorrow.

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Doc Al

Mentor
Re: Amount of charge flowing through a resistor???

for the first one, i have no idea. i cant seem to find any formula that is relavent to this so im guess the answer is simple but im missing a vital piece of information that would link the dots.
What's the definition of current?

for the second one i was thinking the power disippated in the resistor would be the same as the resistance, becuase the resistance is stopping anything above 2.0 V to enter the resistor?
No, power is not the same as resistance. But the power dissipated depends on the current and the resistance. (Look it up!)

druuuuuuuunnk

Re: Amount of charge flowing through a resistor???

What's the definition of current?
"Electrical current is a measure of the amount of electrical charge transferred per unit time. It represents the flow of electrons through a conductive material.
Current is a scalar quantity (though in circuit analysis, the direction of current is relevant). The SI unit of electrical current is the ampere, defined as 1 coulomb/second"

so its 600 coulombs

im still confused about power, i've tried looking it up but it doesnt make any sense, is it the same as voltage?

so V=IxR

meaning 3 mA x 2 kΩ giving me 6 Volts that are being dissapated in the resistor

Doc Al

Mentor
Re: Amount of charge flowing through a resistor???

"Electrical current is a measure of the amount of electrical charge transferred per unit time. It represents the flow of electrons through a conductive material.
Current is a scalar quantity (though in circuit analysis, the direction of current is relevant). The SI unit of electrical current is the ampere, defined as 1 coulomb/second"
Current = Charge/Time, thus Charge = Current * Time.

so its 600 coulombs
Redo that calculation.

im still confused about power, i've tried looking it up but it doesnt make any sense, is it the same as voltage?

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druuuuuuuunnk

Re: Amount of charge flowing through a resistor???

Ok so, to find the charge in 200 seconds. I multiply 3mA by 200 because charge = current*time

Giving me 600A ??

And for the second part I use Power = voltage * current

So the power dissipated in the resistor = 600 (current) * 2 (resistance) is this wrong ?

druuuuuuuunnk

Re: Amount of charge flowing through a resistor???

Actually for the second part, I'm meant to use power = current squared * resistance. So I'd get 720,000

Doc Al

Mentor
Re: Amount of charge flowing through a resistor???

Ok so, to find the charge in 200 seconds. I multiply 3mA by 200 because charge = current*time

Giving me 600A ??
Careful: mA means milli-Amps = 10-3 Amps

(And the charge would be in Coulombs, not Amps.)

Same issue with your power calculation.

druuuuuuuunnk

Re: Amount of charge flowing through a resistor???

Ok, cheers mate!

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