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If a fan is rated at 3 amps at 220 volts what would be the amp rating at 440 volts?
The rating of 3A and 220V is the power rating. It's a bit strange that it's not being expressed in Watts, but it's not hard to figure out. Power is the measure of energy over time being passed through the circuit. Without getting into the particulars, you can express power as P=VI, where P is power in watts, V is voltage in volts, and I is current in amps. So in your case, power is equal to P=(220V)(3A), which equals P=660W. So if we take this and plug it into our new equation where V is doubled, we get (220V)(3A)=(440V)(I) where I is the amperage rating we're looking for. Algebra tells us that this equation now equals I=(660W)/(440V), which equals I=1.5A. So your answer is 1.5A. Basically all you have to remember is that as long as power is constant, voltage and amperage are inversely related. If you double volts, you have to halve amps. <<>> While it's true that a fan designed for 440 volts would use half the current of one designed for 220 v if they both use the same power, it is not possible to take a 220 v fan and plug it in to 440 v, which would definitely cause overheating and maybe a blown fuse or possibly a fire.
What is the resistance when a 660w electric heater is operated from a 120v lines?
We have to work this problem on a DC basis, since we know nothing about the power factorof the supply, or the reactance of the heater.Power in the load = E2 / R.So R = E2 / P.R = (120)2 / 660 = 21.82 ohms (rounded)That's the resistance of the heater ... as the question is worded, it's not clear that thequestioner understands this.
