Does the heating element in something like an electric hot water heater have high resistance or low resistance? I can't seem to find the answer the to that question. If it has low resistance , then why does the filament of a incandescent light bulb have high resistance?

 

Heaters and lightbulbs have low resistance.

For example , a 100W bulb. P = V^2/R

R = V^2/P
= 144 Ohms

1000W heater
R = 120^2/1000
= 14.4 Ohms

Keep in mind that this resistance is 'dynamic'. During startup, there is a much lower resistance seen. This is because as the filament heats, it's resistance increases. Therefore, the current goes down.

Steve

 

I thought about that a bit more, and the answer is relative. Yes, the lightbulb's filament is high resistance in comparison to the wire used to connect it to the AC supply. But, it's certainly not high in comparison to a typical resistor used in an opamp circuit.

Steve

 

could you pls tell me what an opamp circuit is?

 

how about a thank you for answering your original question?

 

hey... I dint mean that to be rude or anything... I really dont know what an opamp circuit is.. thanks anyway

 

Hello,

A lot of information on electronic components and circuits can be found in the EDUCYPEDIA.
http://www.educypedia.be/electronics/electronicaopening.htm
For opams take a special look at this PDF : http://www.standardics.philips.com/support/documents/analog/pdf/an165.pdf

Greetings,
Bertus

 

could you pls tell me what an opamp circuit is?

You could start by having a look at our Op Amps section in the e-book: http://www.allaboutcircuits.com/vol_3/chpt_8/index.html

Dave

 

"Does the heating element in something like an electric hot water heater have high resistance or low resistance?"

Yes! Next question, please...

More seriously:
Hi or low compared to what?

It will have the resistance required to dissipate the required power. It will be higher than the resistance of a penny but lower than the resistance of a 100 watt light bulb.