Circuit with switch resistors and capacitor

In summary, in the given circuit with a switch rotated from contact a to b, the upper plate of the capacitor has a charge of 80 V, the current is determined by dividing the initial charge by the product of the resistance and capacitance, the time constant is determined by the product of the resistance and capacitance, and the charge on the upper plate of the capacitor after 7.00 ms is determined by the initial charge and the time constant.
  • #1
hitman0097
31
0

Homework Statement


For the circuit shown in the figure below, C = 7.50 µF, script e = 80 V, and R = 400 Ω. After having been at contact a for a long time, the switch throw is rotated to contact b.
25-p-095-alt.gif


a.)What is the charge on the upper plate of the capacitor just as the switch throw is moved to contact b?

b.)What is the current just after the switch throw is rotated to contact b?

c.)What is the time constant of this circuit?

d.)How much charge is on the upper plate of the capacitor 7.00 ms after the switch throw is rotated to contact b?

Homework Equations


I=V/R
Inet=V/Req
C=Q/V

The Attempt at a Solution


I have no idea...at all.
 
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  • #2
I really need so type of help.
 
  • #3
anyone?
 
  • #4
When the switch is in the position a for a long time, potential across the capacitor is 80 V.
Qo = CV.
Io = Qo/RC.
RC is the time constant.And using
Q = Qo*e^-t/RC
find Q.
Don't you have any textbook? Didn't you see these equations in the book? Are you not willing to open the book and go through the chapter on capacitor?
 
  • #5
It helps to remember that the charge stored on a capacitor can't jump instantaneously to a new value, and therefore the voltage across a capacitor can't jump instantaneously to a new value. Both of these have an exponential decay from their initial to their final values. This will put a constraint on the resistor current immediately after the switch is thrown.
 

What is a circuit with a switch, resistors, and capacitor?

A circuit with a switch, resistors, and capacitor is a type of electrical circuit that allows for the control of current flow using a switch. Resistors are used to limit the flow of current, while a capacitor is used to store and release electrical energy.

How does a switch work in a circuit?

A switch is a device that opens or closes a circuit, allowing or blocking the flow of electricity. When the switch is open, the circuit is broken and no current can flow. When the switch is closed, the circuit is complete and current can flow through it.

What is the purpose of resistors in a circuit?

Resistors are used in a circuit to limit the flow of current. This is important because some components in a circuit may be sensitive to high levels of current and can be damaged if not regulated. Resistors also help to control the voltage and can be used to divide the voltage in a circuit.

How does a capacitor store and release energy?

A capacitor is made up of two conductive plates separated by an insulating material. When a voltage is applied to the capacitor, one plate becomes positively charged and the other becomes negatively charged. This creates an electric field between the plates, storing energy. When the capacitor is discharged, the stored energy is released as a current.

How do I calculate the total resistance in a circuit with resistors in series and parallel?

To calculate the total resistance in a circuit with resistors in series, you simply add up the individual resistances. In a parallel circuit, the total resistance is calculated using the formula 1/Rt = 1/R1 + 1/R2 + 1/R3... where Rt is the total resistance and R1, R2, R3 are the individual resistances.

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