Hi everybody, I am a freshman college student who is greatly interested in electrical circuits for my major in hardware engineering but I am struggling on my first homework assignment for my ELEC 1300 class.
This is my first post but since I have found out about this forum, I hope to continue posting and contribute back to the community as I learn more, in return for the help others can offer me.
I only say this because I don't want the community to think I'm just trying to get some quick answers to get me by in the class with no work done on my own part.
I would like to included a short bit of background on myself to help you help me. The highest form of math I have taken as of yet is Pre-calculus my senior year in high school. When choosing my courses for college, the prerequisite for this electric circuits class was only pre-calculus so I thought I would be fine, however once I started, the professor told us we would be using calculus from day 1. I'm still slightly confused about integrals and know that I need to understand them to solve many of the problems. I say this because if integrals are involved in either of these questions, I would greatly appreciate if you could explain why and how you used integrals to solve.
With that said, here are my two questions (They are relatively unrelated so I only posted one in the subject line)
The first question I have, I did a search and found a forum already posted with a very similar question, however, I was confused by the answer provided and was wondering if somebody could help explain better. Here is the link if you would like to check it out first: http://forum.allaboutcircuits.com/showthread.php?t=28331&highlight=assume+charge+upper+terminal
1.) The current entering the upper terminal of Fig. 1.5. (Included in pdf and jpeg as attachment) is "i = 20cos5000t A."
Assume the charge at the upper terminal is zero at the instant the current is passing through its maximum value. Find the expression for q(t).
I'll be honest and say I don't understand anything about this question. I have been paying attention during class and am positive the professor hasn't mentioned finding expressions for q(t) and cos was never involved in any work we did.
I know I'm suppose to show my attempts so my only guess as to what I'm trying to do here is solve for 'q', since I am given 'i' and 't' and I know "q = it", however, 't' is already included in current given so I am completely lost. Basically, I don't know what it means when it says "Find the expression for q(t)". Sorry I can't provide any other knowledge about the problem but this just left me completely confused. Also, the answer in the back of the book is "4sin5000t mC" but I have no idea how this answer could be reached.
My second problem I understand a bit more and could take a guess but am near positive I would be wrong.
2.) The manufacturer of a 1.5 V D flashlight battery says that the battery will deliver 9 mA for 40 continuous hours. During that time the voltage will drop from 1.5 V to 1.0 V. Assume the drop in voltage is linear with time.
How much energy does the battery deliver in this 40 h interval?
I'm trying to solve for 'J' (energy) and I am given 'V', 'T', and "i". Thus, I assume I can use the power formula P = (w/t) = VI.
First I convert my units, so
9mA = .009A
40h = 144000s
Also, if V drops from 1.5 to 1.0 over time, I assume I should use 1.25 as V?
Solving for P I get (1.25)x(.009) = .01125W
Now using P = (w/t) I get .01125 = (w/144000) which comes out to w=1620J
Thank you very much in advance for any help you can offer me and sorry about the excessive text at the top. Hopefully it shows that I'm really interested in being part of the community and am not just here this once begging for answers.
This is my first post but since I have found out about this forum, I hope to continue posting and contribute back to the community as I learn more, in return for the help others can offer me.
I only say this because I don't want the community to think I'm just trying to get some quick answers to get me by in the class with no work done on my own part.
I would like to included a short bit of background on myself to help you help me. The highest form of math I have taken as of yet is Pre-calculus my senior year in high school. When choosing my courses for college, the prerequisite for this electric circuits class was only pre-calculus so I thought I would be fine, however once I started, the professor told us we would be using calculus from day 1. I'm still slightly confused about integrals and know that I need to understand them to solve many of the problems. I say this because if integrals are involved in either of these questions, I would greatly appreciate if you could explain why and how you used integrals to solve.
With that said, here are my two questions (They are relatively unrelated so I only posted one in the subject line)
The first question I have, I did a search and found a forum already posted with a very similar question, however, I was confused by the answer provided and was wondering if somebody could help explain better. Here is the link if you would like to check it out first: http://forum.allaboutcircuits.com/showthread.php?t=28331&highlight=assume+charge+upper+terminal
1.) The current entering the upper terminal of Fig. 1.5. (Included in pdf and jpeg as attachment) is "i = 20cos5000t A."
Assume the charge at the upper terminal is zero at the instant the current is passing through its maximum value. Find the expression for q(t).
I'll be honest and say I don't understand anything about this question. I have been paying attention during class and am positive the professor hasn't mentioned finding expressions for q(t) and cos was never involved in any work we did.
I know I'm suppose to show my attempts so my only guess as to what I'm trying to do here is solve for 'q', since I am given 'i' and 't' and I know "q = it", however, 't' is already included in current given so I am completely lost. Basically, I don't know what it means when it says "Find the expression for q(t)". Sorry I can't provide any other knowledge about the problem but this just left me completely confused. Also, the answer in the back of the book is "4sin5000t mC" but I have no idea how this answer could be reached.
My second problem I understand a bit more and could take a guess but am near positive I would be wrong.
2.) The manufacturer of a 1.5 V D flashlight battery says that the battery will deliver 9 mA for 40 continuous hours. During that time the voltage will drop from 1.5 V to 1.0 V. Assume the drop in voltage is linear with time.
How much energy does the battery deliver in this 40 h interval?
I'm trying to solve for 'J' (energy) and I am given 'V', 'T', and "i". Thus, I assume I can use the power formula P = (w/t) = VI.
First I convert my units, so
9mA = .009A
40h = 144000s
Also, if V drops from 1.5 to 1.0 over time, I assume I should use 1.25 as V?
Solving for P I get (1.25)x(.009) = .01125W
Now using P = (w/t) I get .01125 = (w/144000) which comes out to w=1620J
Thank you very much in advance for any help you can offer me and sorry about the excessive text at the top. Hopefully it shows that I'm really interested in being part of the community and am not just here this once begging for answers.
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