How Do You Calculate the Voltage Drop Across a 100 Watt Light Bulb?

[lespaul5895]

Right now I'm a first year electrical engineering student at Purdue University. I have a problem that I have to do for a homework assignment I read the entire chapter and cannot find out how to do this problem. Any help would be appreciated, if this isn't the right place to ask this question just let me know and if not I would appreciate any information on how I could find help.

A 100 watt light bulb dissipates 100 joules of energy per coulomb of charge. Find its voltage drop.

Thanks in advance.

 

[Astronuc]

Have you learned the relationship between power, voltage and current?

Also 1 V = 1 J/C = 1 W/A.

http://en.wikipedia.org/wiki/Volt

The volt is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepow.html
http://en.wikipedia.org/wiki/Electric_power

Real Power = Voltage * Current = V*I = V²/R = I²*R

 

[lespaul5895]

call me dense but I don't see the relationship there, I don't see how those equations relate to the problem given. Most of those deal with current and resistance, please explain. sorry I'm kinda slow when it comes to learning stuff and I want to make sure I fully understand this.

edit: So what you're saying is that 1Watt = J/C? so the equation would read 100w = 100J/1C = 100V?

 

[Astronuc]

I was showing that 1 V = 1 J/C and so 100 V = 100 J/C.

Now, 1 W = 1 J/s, and if 100 W dissipates 100 J/C, that implies (100 W)/(100 J/C) = (100 J/s)/(100 J/C) = 1 C/s = 1 A.

So for a 100 W light bulb to dissipate 100 J/C, the voltage drop is 100 V, and the current is 1 A.


See also - http://science.howstuffworks.com/question501.htm
What are amps, watts, volts and ohms?