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14 years ago

I have a whole bunch of homework and I don't know how to do it!!!!! I was going to ask my teacher but it's late already... so ya. But I have some odd questions like:
"A clothes dryer uses a 220 V power source. The coils of the heater procide an average resistance of 12 ohms. What amount of current is flowing through the heating coils?" I don't want just a simple answer I would appreciate it if you explained it to me how to answer questions like this, NOT just the answer.
I will need to know the formulas for getting:
Power, Resistance, Current, Time, Energy, Potential Difference, and Charge. thanks a bunch!!!

Top 3 Answers

14 years ago

Favorite Answer
It sound's like you're doing simple calcs, where you can assume that current remains proportional to voltage (in practise they end up "out of sync" with AC- but that involves complex numbers/vectors- and you'd know if that's what you have to usu!)
Think you need the following, and need to apply/rearrange/combine the following equations
V=I*R
P=V*I=I*I*R
E= P * t = I*I*R*t
V= Potential difference across component/supply terminals (Volts)
I= Current THROUGH component (Amps)
R= Resistance of component (Ohms)
P= Power of component (Watts)
E= Energy used by component (Joules)
The only bit I can remember about charge is how to relate it to capacitance,voltage, and time.
http://en.wikipedia.org/wiki/Capacitor#Energy_storage
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For question you've given you have voltage and resistance and need to find the unknown of current.
V=220 [V]
R= 12 [ohms]
calculate current by application of Ohm's Law....
V[Volts]=I[Amps]*R[Ohms]
I[Amps]=V[Volts]/R[Ohms]
I[Amps= 220 [Volts] /12 [Ohms[
I= 18 + 1/3 Amps
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It doesn't state the power source is AC or DC- I've assumed it's DC. For AC the (simple) answer is the same, but only so long as the 220 V referes to the RMS value of the voltage (as a RMS voltage is a "kind" of average voltage as used for AC)

1

7 years ago

Voltage is a potential of electrical flow (concentrated charge relative to the rest of the circuit. Current is the flow of electrons. As the current flows, the voltage drops, unless resupplied. Resistance is the resistance o the current flow. More resistance, more voltage drop across the resistor (the resistor burns up electrical potential). Power is rate at which electrical energy is being used. Charge is the quality of an electron which allows it to be pushed through a circuit by applied voltage and its associated electric field. Joules is a measure of energy. This can include electrical energy [e.g., (i^2R)t].

0

14 years ago

E=IxR
P=IxE
P=I^R
I=E/R
220/12=I

1

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