Thanks a lot! You two answered a lot of questions I'd had in mind for a long time!
Voltage is the common (and shorter) term for electromotive force, which is measured in units of volts. It's a different kind of force than mechanical force, in that it applies only to electrical charge.
Electrical charge, which is measured in units of coulombs, is the characteristic that electrons and protons have that causes them to interact with voltage. There are about 6.242×1018 electrons in a charge of -1 coulomb. Notice that the charge of electrons is negative, for historical reasons.
Current is the rate of flow of charge, measured in amperes. An ampere is 1 coulomb per second.
Power is the rate of flow of energy, measured in watts. In an electrical circuit, the power is the product of voltage and current. The flow of energy between a power source and a load is in the direction of the current flowing in the wire with the more positive voltage, from the source to the load. In the US, we reserve the watt for electrical power and use other units, like horsepower and BTUs per hour; but the rest of the world tends to use the metric unit of the watt for all kinds of power.
A resistor is a circuit element for which the voltage across the element is proportional to the current flowing through it. This proportionality is called resistance and is expressed in volts per ampere, which is the definition of the ohm. (One ampere per volt, on the other hand, is a siemens.) If the voltage and current are not proportional, which is often the case, the element is not a resistor.
Bob Nelson
I'm not an electrician, and I don't know much about electricity. Does anyone know where I can find a quick reference in layman's terms that detail the relationship between watts, volts, amps, and ohms? I've never known exactly how much drain there is on the transformers I use when connecting accessories and running operating cars with lights.
Was bridgeengineer's calculation correct?
MTH indicates the power is 10 amps per throttle.
Larry
They are independent. 10 amps per side.
Rob
We know that a Lionel ZW conventional transformer can deliver its maximum power through any one of its four throttles, because all four of them roll over the same secondary coil of the transformer. After losses due to transformation and efficiency, the 275-watt-rated transformer can deliver roughly 190 to 195 watts on a continuous basis. My question resulted from operation of a heavy train on a MTH Z-4000 transformer, rated at 400 watts. When a lightweight train is operated, the built-in ammeter may show something like 2 amps, and if you crank up the throttle all the way, the voltmeter may go up to almost 21 volts. I put on a train consisting of a Lionel 2343 F3, a 2333 F3, and nine AMT aluminum passenger cars. The locos each have two motors and a light bulb, and the cars each have two light bulbs. Using wattage tables for the motors and bulbs from old Lionel instruction books, I estimated the wattage draw for this train could be in the range of 160 to 200 watts. When run on a Z-4000, the ammeter shuttled between 9.3 and 9.4 amps, and with the throttle all the way up, the voltmeter would not go past 16 volts. Multiplying volts times amps, I interpreted this to mean that the throttle was putting out about 150 watts. So, are the two sides of a Z-4000 independent of each other, each only able to deliver half of the total rated power, after transformation losses?
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