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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Electric Current in Conductors

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Electric Current in Conductors

The amount of charge passing through a cross-section of a wire in...

The amount of charge passing through a cross-section of a wire in time tt is Q(t)=At2+Bt+CQ(t) = At^2 + Bt + C. Assuming the numerical values of AA, BB, and CC in SI units are 55, 33, and 11 respectively, find the value of the current at t=5 st = 5 \text{ s}.

Options

  1. A141 A141 \text{ A}
  2. B53 A53 \text{ A}
  3. C28 A28 \text{ A}
  4. D25 A25 \text{ A}

Correct answer

B. 53 A53 \text{ A}

Step-by-step solution

Given the charge passing through the cross-section as a function of time:

Q(t)=At2+Bt+CQ(t) = At^2 + Bt + C

The current II is the rate of flow of charge, given by the derivative of Q(t)Q(t) with respect to time tt:

I(t)=dQdt=ddt(At2+Bt+C)=2At+BI(t) = \dfrac{dQ}{dt} = \dfrac{d}{dt}(At^2 + Bt + C) = 2At + B

Substituting the given numerical values A=5A = 5 and B=3B = 3:

I(t)=2(5)t+3=10t+3I(t) = 2(5)t + 3 = 10t + 3

At t=5 st = 5 \text{ s}, the current is:

I(5)=10(5)+3=50+3=53 AI(5) = 10(5) + 3 = 50 + 3 = 53 \text{ A}
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