Solving 2 Loop RC Circuit: Find I1(0)

AI Thread Summary
The discussion centers on calculating the initial current I1(0) through resistor R1 in a circuit with resistors, a capacitor, and a battery after closing a switch. It is established that the capacitor's voltage is zero immediately before and after the switch is closed, as capacitors resist instantaneous changes in voltage. The relationship between currents in the circuit is clarified, with I2 equating to I3 and I1 equating to I4. The participants emphasize that the capacitor will eventually reach a steady state determined by the surrounding resistor network. Understanding these principles is crucial for solving the circuit problem effectively.
kjlchem
Messages
23
Reaction score
0

Homework Statement



A circuit is constructed with four resistors, one capacitor, one battery and a switch as shown. The values for the resistors are: R1 = R2 = 49 Ω, R3 = 64 Ω and R4 = 64 Ω. The capacitance is C = 88 μF and the battery voltage is V = 24 V.

The switch has been open for a long time when at time t = 0, the switch is closed. What is I1(0), the magnitude of the current through the resistor R1 just after the switch is closed?


Homework Equations



C = Q/V
V=IR

The Attempt at a Solution



Currents in series are the same, so I2=I3. Currents going into a junction = currents coming out so, I1=I4. I think it might all be the same current.

V= I1(R1+R4) + Q/C
Q/C=(R2+R3)I2

I don't know how to find Q/C or I2.
 
Physics news on Phys.org
Forgot to attach the diagram!
 

Attachments

  • rdc.png
    rdc.png
    1.3 KB · Views: 711
Immediately before the switch is closed, what's the voltage (and charge) on the capacitor?
What then is the voltage on the capacitor immediately after the switch is closed?
 
The voltage on the capacitor before the switch is closed is 0, I believe . After it is = To the v at the battery
 
kjlchem said:
The voltage on the capacitor before the switch is closed is 0, I believe . After it is = To the v at the battery

Not quite. It is zero immediately before and therefore immediately after the switch is closed, too.

Capacitors have a sort of inertia... they won't let their potential differences change instantaneously (much as inductors won't allow the current flowing through them to change instantaneously).

After some long period of time the voltage on the capacitor will eventually reach some steady state value as determined by the resistor network surrounding it.
 
Cool! I did not know that. Thank you!
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Back
Top