Math Problem Statement

Find out the voltage at t=9.5sec across the capacitors if the switch is closed at t=9sec. Write down the expression for the current across the 2K resistor. Draw the T vs IR=2K and T vs VR=2K graphs. Draw the T vs VAB graph for t starting from 0sec to 12sec.

Solution

To solve the problems based on the provided circuit diagram, we need to break down each part of the question. Here's a step-by-step analysis for parts D through G.

Part D: Voltage across capacitors at t=9.5t = 9.5 sec

  • Before t=8t = 8 sec: The capacitors were connected to a different circuit. We assume that they were charged to some voltage. Once they are disconnected and the new circuit is connected at t=9t = 9 sec, we need to find the voltage across the capacitors at t=9.5t = 9.5 sec.
  • Capacitance: The two 10μF10 \mu F capacitors are in parallel, giving an effective capacitance Ctotal=20μFC_{\text{total}} = 20 \mu F.
  • Discharging Behavior: When the switch closes at t=9t = 9 sec, the capacitors will start discharging through the resistors.

We assume the discharge will follow an exponential decay: V(t)=V0etRCV(t) = V_0 \cdot e^{-\frac{t}{RC}} where:

  • V0V_0 is the initial voltage across the capacitors (just before t=9t = 9 sec),
  • RR is the total resistance the capacitors are discharging through,
  • CC is the total capacitance,
  • tt is the time after the switch is closed.

To calculate this fully, we would need more information about the initial conditions or the configuration before t=8t = 8 sec. Otherwise, we'd proceed by calculating assuming a typical setup.

Part E: Current across the 2kΩ resistor

For the current through the 2kΩ resistor after the switch closes at t=9t = 9 sec, we use Ohm's Law: IR2=VR2R2=V(t)2000I_{R_2} = \frac{V_{R_2}}{R_{2}} = \frac{V(t)}{2000} where V(t)V(t) is the voltage across the 2kΩ resistor, which depends on the charge remaining in the capacitors as they discharge.

Part F: Graph of TT vs IR=2kI_{R=2k} and TT vs VR=2kV_{R=2k}

These graphs will follow an exponential decay since the current and voltage in an RC discharging circuit follow this behavior:

  • I(t)I(t) and V(t)V(t) both decay exponentially with time, as described in Part E.

The general form of the voltage and current will be: V(t)=V0etRCandI(t)=I0etRCV(t) = V_0 e^{-\frac{t}{RC}} \quad \text{and} \quad I(t) = I_0 e^{-\frac{t}{RC}}

Part G: TT vs VABV_{AB} graph

This graph will also be similar to the voltage and current curves in an RC discharging circuit, with the voltage across the capacitors decreasing over time according to an exponential function.

To fully solve these problems and draw the graphs, I can help compute numerical values if more information (such as initial voltage) is provided. Would you like to proceed with some assumptions for the missing data, or provide additional details for further calculation?

Follow-up Questions:

  1. What was the initial charge on the capacitors before they were disconnected at t=8t = 8 seconds?
  2. Should we assume that the capacitors were fully charged before being connected to the new

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Math Problem Analysis

Mathematical Concepts

Circuit analysis
Exponential decay
Capacitance
Ohm's Law

Formulas

V(t) = V0 * e^(-t/RC)
I = V/R

Theorems

Ohm's Law
Capacitor Discharge Equation

Suitable Grade Level

Undergraduate-level Electrical Engineering