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# Wattage Of A Device

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#### Electroenthusiast

##### Active Member
What exactly is responsiple for wattage of a device?
why does a water hearter has 1000's in wattage, whereas a bulb is just 20-100 watts?
Do they have lower resistance compared to lower wattage devices?...Because voltage is always constant but only current varies!

I want to make it clear that how the Wattage of a Device Depend on?, and how the higher wattage devices pull more current (Practically)?

A water heater is usually made from a thick wired copper tube connected to the heater power. The lower copper resistance per meter makes it a very small resistance, which will draw a large current.

The light bulb is made from e.g. wolfram wire together with a glass bulb with vacuum. It takes a lower current to make the wire glow, and some (not a lot) of the energy is converted to light, and not heat as the water heater.

Learn and understand I=E/R and P=I*E

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the Wattage of a Device Depend on ?
you should be understanding in Watt's Law states the relationships of power to current, voltage and resistance.
So, Power(watt)=voltage*current

Guys.... I want a practical explanation... not theoretical : P= IV !

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Mike's right you need to learn basic electricity math. Then it'll make sense.

Learn and understand I=E/R and P=I*E

Put 'em together and you get P=E²/R

So power (watts) go up when voltage goes up (exponentially), and goes down when resistance goes up.

So, for a given voltage, a high-watt device shows a lower resistance (or impedance) in the circuit than a low-watt device.

Clear as mud?

As for why a water heater has a lower resistance and thus draws more power than a light bulb... because it's designed to. It takes more energy to heat 40 gallons of water than to light up a room. One could make a 100 watt water heater but the water would take a really long time to heat. You could stick a 1000 watt bulb in your ceiling fixture but you'd go blind, melt the fixture and burn your house down all in one easy step.

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To reply simply. Yes, at the same voltage, a higher wattage device has a lower resistance. A lower wattage device has a higher resistance.

Put 'em together and you get P=E²/R

So power (watts) go up when voltage goes up (exponentially), and goes down when resistance goes up.

So, for a given voltage, a high-watt device shows a lower resistance (or impedance) in the circuit than a low-watt device.

Clear as mud?

As for why a water heater has a lower resistance and thus draws more power than a light bulb... because it's designed to. It takes more energy to heat 40 gallons of water than to light up a room. One could make a 100 watt water heater but the water would take a really long time to heat. You could stick a 1000 watt bulb in your ceiling fixture but you'd go blind, melt the fixture and burn your house down all in one easy step.

Thanks ... i really liked your explanation !

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