Very basic circuits 1 question. Charge and current

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SUMMARY

The discussion centers on calculating the charge q(t) flowing through a device given the current i(t) = 20 cos(10t + π/6)μA and the initial charge q(0) = 2 μC. The correct solution for q(t) is derived as (2sin(10t + π/6) + 1)μC, which incorporates the initial charge correctly. The confusion arose from misinterpreting the integration of the current and the initial condition, leading to an incorrect addition of q(0) in the final expression. Clarification was provided on how to properly integrate the current to obtain the charge function.

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  • Understanding of basic circuit theory
  • Knowledge of calculus, specifically integration
  • Familiarity with current and charge relationships in electrical circuits
  • Ability to interpret and manipulate trigonometric functions
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  • Review integration techniques for electrical engineering applications
  • Study the relationship between current and charge in circuits
  • Learn about the role of initial conditions in differential equations
  • Explore trigonometric identities and their applications in circuit analysis
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Students studying electrical engineering, particularly those preparing for exams in circuit analysis and differential equations. This discussion is also beneficial for educators seeking to clarify integration concepts in the context of electrical current and charge.

A.J.710
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Homework Statement


Find the charge q(t) flowing through a device if the current is: 20 cos(10t + π/6)μA, q(0) = 2 μC

Homework Equations


∫ i(t)dt +q(0)

The Attempt at a Solution


I am studying for a test by working all the problems I can and then looking at the solutions manual. The solutions manual says the answer is (2sin(10t+π/6)+1)μC. I got the same thing except +2 at the end since q(0) is 2. It's really bugging me that I can't figure out why. Can anyone please explain?
 
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A.J.710 said:
The solutions manual says the answer is (2sin(10t+π/6)+1)μC. I got the same thing except +2 at the end since q(0) is 2.
If you plug in t = 0 to your solution and the manual's, which one gives the correct answer?
 
Doc Al said:
If you plug in t = 0 to your solution and the manual's, which one gives the correct answer?
Ahh, got it now. Thank you. I didn't realize that's what it meant. I was just adding the q(0) but I didn't realize until you pointed it out that the entire function in itself is q.
 

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