I know that if I needed 600 watts at 120 volts that I would need at least 5 amps, but does the step down create a difference in amperage when using a transformer converting the 120v. to 12v?
A circular saw is an AC circuit. If you were using a DC circuit, you would be using a 1200 watt tool since all of the electricity (subtracting heat loss of course) is used to run the tool. In an AC circuit, the AC is 'alternating current', a sine wave. Only a portion of the sine wave is used for real work. The rest is used to establish and collapse magnetic fields. This term is known as 'Root Mean Square' or RMS and has to be taken into account for the problem. The value of RMS in a typical 120 volt, 60 Hz circuit is .707 or 70.7% of usable energy in the sine wave. So this leads us to the question, how many watts? Answer(120V * 10A).707 848.4W. The next one is easy, they are already watt rated so there's no conversion. 1000 Watts * 8 hrs 8KWH. 8 cents * 8 KWH 64 cents. Hope this helps.
This Site Might Help You. RE: If I have a 600 watt 12 volt transformer plugged into a 120 volt circuit, what 120v. amperage is needed? I know that if I needed 600 watts at 120 volts that I would need at least 5 amps, but does the step down create a difference in amperage when using a transformer converting the 120v. to 12v?
A 120 volt-to-12 volt step down transformer has a 10:1 ratio. This means that the voltage coming OUT of the transformer will be 10 times less than the voltage going IN, and the amperage coming OUT the transformer will be 10 times more than the amperage going IN. If you connect a 60 watt 12 volt car headlight bulb to the output of your transformer, there will be 5 amps flowing from the transformer to the bulb, but only 1/2 an amp flowing from your wall outlet into the transformer. If you connect 2 bulbs, you would have 10 amps coming out, and 1 amp going into the transformer. If you connect 10 bulbs, you would have 50 amps coming out, and 5 amps going into the transformer, which would be the max for your transformer. As you can see, if you have less voltage, you need more amperage to do a given amount of work. A 60 watt household light bulb needs 1/2 an amp at 120 volts, and a 60 watt automotive bulb needs 5 amps at 12 volts. Both bulbs use the same amount of power and provide the same amount of light. Amps times volts equals watts. Watts is the actual amount of power being consumed, regardless of what the voltage or amperage is. You pay for electricity in watts per hour.
600 watts at 120 volts is, as you have calculated, equals 5 amperes. Yes, if the transformer were 100% efficient, the secondary would be able to supply 600 watts at 12 volts, or 50 amps. Let's assume it's 70% efficient; that would still allow it to deliver 35 amps.
