Which is the constant of differentiation?

[Calpalned]

When the textbook differentiated with respect to time, I see that the middle term is R(dI/dt). Why can't it be I(dR/dt)? When I differentiate, how do I know which letter to differentiate?
3. The Attempt at a Solution
2. Homework Equations
1. Homework Statement

 

[LCKurtz]

View attachment 90516
When the textbook differentiated with respect to time, I see that the middle term is R(dI/dt). Why can't it be I(dR/dt)? When I differentiate, how do I know which letter to differentiate?

The Attempt at a Solution

Homework Equations

Homework Statement

L, R, and C are constants. You are differentiating with respect to time and the constants don't vary.

 

[SammyS]

View attachment 90516
When the textbook differentiated with respect to time, I see that the middle term is R(dI/dt). Why can't it be I(dR/dt)? When I differentiate, how do I know which letter to differentiate?

The Attempt at a Solution

Homework Equations

Homework Statement

Why did you ignore the template? You even went through the trouble to change the font color.

To answer your question:

R is a constant just like L and C. You had no objection to treating them as constants.

 

[Calpalned]

L, R, and C are constants. You are differentiating with respect to time and the constants don't vary.

I see... If I look at the original equation (1.2) has $\frac{dI}{dt}$ and that tells me that I is not a consant?

 

[SammyS]

I see... If I look at the original equation (1.2) has $\frac{dI}{dt}$ and that tells me that I is not a consant?

Actually, it helps to understand something of the physics behind this problem.

V is voltage or emf. I is current.

 

[Calpalned]

Actually, it helps to understand something of the physics behind this problem.

The example was on differential equations in general, so the textbook didn't give me background information on the physics.

 

[NascentOxygen]

The example was on differential equations in general, so the textbook didn't give me background information on the physics.

You could use the product rule, differentiating the product RI w.r.t. time. What result would you get?