Rate of change of current with time, galvanometer deflection

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Homework Help Overview

The discussion revolves around the concepts of inductance in solenoids, the behavior of current in a series R-L circuit, and the calculation of galvanometer deflection in response to changing current. Participants explore the implications of inductance values and the relationships between voltage, current, and resistance in electrical circuits.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants attempt to derive the final current and the rate of change of current at specific instances, questioning how to express current as a function of time and how to differentiate that function to find rates of change.

Discussion Status

The discussion is active, with participants providing guidance on the step response of R-L circuits and suggesting the use of specific formulas. There are multiple interpretations of the problem, particularly regarding the calculation of current and the conditions under which certain values apply.

Contextual Notes

Some participants express uncertainty about the application of formulas and the underlying assumptions, particularly regarding the behavior of the circuit when the current is switched off and the definitions of variables involved.

  • #61
Bingo. Calculate the right side with numbers and you are done.
 
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  • #62
kuruman said:
Bingo. Calculate the right side with numbers and you are done.
B = μ0 n I = 4 π * 10-7 * 1000 * 4 = 5 * 10-3 T.
Q = 2000 * (8 * 10-4) * (5 * 10-3) / 60 = 1.33 * 10-4 C
 
  • #63
moenste said:
Q = Φ / R = B A N / R?
Right.
 
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  • #64
moenste said:
B = μ0 n I = 4 π * 10-7 * 1000 * 4 = 5 * 10-3 T.
Q = 2000 * (8 * 10-4) * (5 * 10-3) / 60 = 1.33 * 10-4 C
That should be 1.34*10-4..
Use sensitivity of the galvanometer to find the number of divisions.
 
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  • #65
cnh1995 said:
That should be 1.34*10-4..
Use sensitivity of the galvanometer to find the number of divisions.
θ = a Q = 2 * 1.34 * 10-4 = 2.68 * 10-4.
 
  • #66
moenste said:
θ = a Q = 2 * 1.34 * 10-4 = 2.68 * 10-4.
Well, 1.34*10-4 is the actual charge passed through the galvanometer. You have sensitivity as 2 divisions/ microcoulomb. How would you calculate the no of divisions from this?
 
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  • #67
cnh1995 said:
Well, 1.34*10-4 is the actual charge passed through the galvanometer. You have sensitivity as 2 divisions/ microcoulomb. How would you calculate the no of divisions from this?
θ = a Q = deflections of the galvanometer.

Update
1.34 * 10-4 C → 1.34 * 10-4 / 10-6 = 134 μC.

134 * 2 = 268. I think this should be right.
 
  • #68
moenste said:
θ = a Q = deflections of the galvanometer.

Update
1.34 * 10-4 C → 1.34 * 10-4 / 10-6 = 134 μC.

134 * 2 = 268. I think this should be right.
Right.
 
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