A ductile metal wire has resistance . What will be the resistance of this wire in terms of if it is stretched to three times its original length, assuming that the density and resistivity of the material do not change when the wire is stretched? (Hint: The amount of metal does not change, so stretching out the wire will affect its cross-sectional area.)
Ch 25: Current, Resistance, and EMF
25장, 문제 7b
The current in a wire varies with time according to the relationship . What constant current would transport the same charge in the same time interval?
검증된 단계별 안내1
First, understand that the problem involves finding a constant current that transports the same charge as a time-varying current over a given time interval.
To find the total charge transported by the time-varying current, integrate the current function I(t) = 55 A - (0.65 A/s^2)t^2 with respect to time over the interval from t = 0 to t = T, where T is the time interval.
The integral of the current function I(t) with respect to time will give the total charge Q transported: Q = ∫(55 - 0.65t^2) dt from 0 to T.
Calculate the integral: Q = [55t - (0.65/3)t^3] evaluated from 0 to T. This will give you the expression for the total charge transported by the time-varying current.
To find the constant current I_c that transports the same charge Q in the same time interval T, use the relationship Q = I_c * T. Solve for I_c by rearranging the equation: I_c = Q / T.

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이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
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주요 개념
질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.
Current and Charge Relationship
Current (I) is the rate at which charge (Q) flows through a conductor. The relationship between current and charge is given by Q = ∫I dt, where the integral of current over time gives the total charge transported. Understanding this relationship is crucial for determining the equivalent constant current that transports the same charge over a given time interval.
추천 영상:
가이드 코스
Intro to Current
Integration in Physics
Integration is a mathematical process used to find quantities like area under a curve, which in physics often represents accumulated quantities such as charge. In this context, integrating the current function I = 55 A - (0.65 A/s^2)t^2 over the specified time interval will yield the total charge transported, allowing comparison with a constant current scenario.
추천 영상:
가이드 코스
Finding Moment Of Inertia By Integrating
Constant Current
A constant current is one that does not change with time, unlike the given variable current. To find a constant current that transports the same charge, one must calculate the total charge transported by the variable current and then determine the constant current that would transport this charge over the same time interval, using the formula Q = I_constant × time.
추천 영상:
가이드 코스
Phase Constant of a Wave Function
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