Electrical question - What is the difference between: wattage, volts, and amps?


homersimpsonlikestrains

homersimpsonlikestrains

Active Member
I'm not an electrician but what is the difference between wattage, volts, and amps? What is the easiest and simplest way to understand this?

For example, each quadrant of my house has a 15 amp maximum. If I use a 10 amp power supply for my G scale train will this come close to blowing out a fuse?
 
No, fuses that are not very old, say 15 years or so (depends on how high the amperage is typically through them. It might not trip them, but if it gets the filament warm/hot much of the time, it degrades the fuse) should be good for pretty much all the way up to their rated amperage.

Voltage is like the pressure from your taps or through your garden sprinklers. More voltage, more water, and more 'throw' at the sprinklers. Wattage is the amount of power consumed by the appliance or instrument. Amperage is the flow, the actual water, or what the unit actually uses to perform work.
 
Selector said:
No, fuses that are not very old, say 15 years or so (depends on how high the amperage is typically through them. It might not trip them, but if it gets the filament warm/hot much of the time, it degrades the fuse) should be good for pretty much all the way up to their rated amperage.

Voltage is like the pressure from your taps or through your garden sprinklers. More voltage, more water, and more 'throw' at the sprinklers. Wattage is the amount of power consumed by the appliance or instrument. Amperage is the flow, the actual water, or what the unit actually uses to perform work.
Click to expand...
Good answer!
 
homersimpsonlikestrains said:
I'm not an electrician but what is the difference between wattage, volts, and amps? What is the easiest and simplest way to understand this?

For example, each quadrant of my house has a 15 amp maximum. If I use a 10 amp power supply for my G scale train will this come close to blowing out a fuse?
Click to expand...
Voltage is the pressure of the electricity. Almost like turning on your garden hose, a certain amount of water coming through it is based on the pressure. If you turn up the pressure at the water meter, then more water comes through because of the higher pressure. Likewise, turn up the voltage, then more electricity comes through the wire because of the higher pressure.

Amps is the amount of electricity passing through the wire. For instance, a 3/4" dia. garden hose allows more water to pass through it than a 5/8" dia. garden hose. A 1" dia. pvc pipe allows even more water yet to pass through it than the 3/4" dia. hose. Likewise again, a bigger diameter electrical wire will allow more electricity to pass through it than a smaller wire will.

Watts is simply a power rating, calculated by multiplying the volts and the amps. For instance, 10 amps x 12 volts = 120 watts. And at the same time, 1 amp x 120 volts also equals 120 watts. 1/10 of an amp (.1 amps) x 1200 volts once again equals 120 watts. You can have a very small diameter of wire that will handle a very large voltage, but it can't handle very much amperage at all. You need to have a bigger wire to allow more amperage, and then you won't need as much voltage to push it through the wire.

Your 10 amp G-scale power supply shouldn't even come close to blowing a 15 amp fuse (or tripping a breaker), provided nothing else on that circuit is currently drawing more than a total of 5 amps of electricity. Chances are even quite good that your 10 amp power supply will not even be using a full 10 amps during operation, anyway. If it is, you need a bigger power supply, and possibly a bigger circuit!
 
And now for the good news, Homer. If you studied and understood my previous post, it's time for some basic math........

I just checked the spec's for an MRC Power G 10 Amp Pack throttle (which is supposedly is discontinued and no longer available). Regardless, it's rated at a maximum of 10 amps continuous output at 22 volts max. DC.

Okay now, 10 amps at 22 volts equals 220 watts of power output. Which means we need 220 minimum watts of power input to supply the output.

Since we have the output watts (220), let's divide it by the voltage (120 volts standard household voltage) to arrive at a figure of 1.833, which is the input amps, or let's round it off to 2 amps. So basically, your 10 amp power supply (output) is really only going to draw about 2 amps (input) of household current to power it at maximum capacity. Maybe even a little more amperage due to power consumption, resistance of wiring, etc. etc., but probably not a whole lot more than 2 amps, so we'll just call it 2 amps.

Actually, since we're only using about 2 amps of electricity on the household circuit, then I was wrong in my previous post :eek::oops: - you need to make sure that no more than 13 amps is not being used at the same time on your household circuit, instead of just 5 amps! So overall, I'd say you'd be pretty safe on a 15 amp circuit. :)👍
 
A household circuit of 15 amps will supply 1800 watts of power when it will trip. 15 amps X 120 volts + 1800 watts.
Your 10 amp transformer puts out 24 volts max. 10 amps X 24 volts = 240 Watts on DC transformers they call it Voltamps
1800 / 240 = 7.5 That circuit will handle 7 transformers at 100%. Are seven safe?, no because you are at the max capacity of that circuit.
 
homersimpsonlikestrains said:
I'm not an electrician but what is the difference between wattage, volts, and amps? What is the easiest and simplest way to understand this?

For example, each quadrant of my house has a 15 amp maximum. If I use a 10 amp power supply for my G scale train will this come close to blowing out a fuse?
Click to expand...
I've read the whole thread and there is really a lot of good information there, but I think this is the simplest answer.

No, the 10 amps output from your train power supply is different than the 10 amps available from your house electrical outlet. Your train power supply does not draw 10 amps from the house, it puts out 10 amps to the track.

The reason is because of the other factors you mentioned, and what everyone else above is explaining. Your house (if you are in the US or Canada) is 110-120 volts which is considered high voltage. When 120 volts pushes 10 amps you get 1,100 watts of power. When your 15 volt (low voltage) train controller pushes 10 amps there is only 150 watts of power.

Finally, I don't see anyone mentioning it. Just because there are 10 amps available, doesn't mean they are used. A locomotive that only draws half an amp will only take the 1/2 amp it needs and ignore the rest. The exception there is a diode. Once it begins to pass electricity it becomes like a short circuit and will attempt to pass the whole 10 amps through.
 
Ok, so some fun.

Y'all are talking about Volts * Amps - and that is VA not Power ( Watts ). You usually see the VA rating on most of the newer electric/electronic stuff. AC power is always a peak value. In other words, true power is Volts * 1.414 * Amps. The 120Vac you measure with most DMM/Volt Meter's is RMS voltage; 120Vac rms is really ~170Vac peak for power calculations. You can buy a peak measuring DMM, but why?

Trivia - Power is the only thing that relates electricity/electronics to our physical world. One horsepower is 745W

Grins....
 
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