Physics

posted by .

Could someone please tell me what equations i am suppose to use to work out these problems.
A capacitor in RC circuit has two overlapping plates of width 3.40 m and length 8.90 m separated by 2.60 cm. A dielectric of dielectric constant being 73.0 fills the space between the plates. A capacitor of 400. ìF is connected in series with a resistor of 13.0 kiloOhms, a perfect switch, and a 28.0 V battery. Initially there is no charge on the capacitor, and the switch is open.
a) What will the voltage across the capacitor be 9.00 s after the switch is closed?
2.The circuit is then left for a long time with the switch closed so that the capacitor fully charges to 28.0 V. The switch is now carefully opened so that no charge leaves the capacitor and the battery is also replaced by a resistor of resistance 11.0 kiloOhms
a) What will be the voltage across the capacitor 20.0 s after the switch is closed again?

  • Physics -

    Is thgis one problem or two?
    In other words is the first capacitor in series with the second and with the resistor?

    For the first capacitor:

    C = e A/d = K eo A/d

    here k = 73
    eo = 8.85 * 10^-12
    A = 3.4 * 8.9
    d = .026

  • Physics -

    If the second problem is the second capacitor in series with the resistor then at the instant the switch is closed the charge on the capacitor is zero and the whole 28 volts appears across the resistor.
    A current flows at that initial instant with value
    Io = E/R = 28/R
    that current fills the capacitor up with charge and as time goes on more voltage appears over the capacitor and less across the resistor so the current goes down. By the time the current is zero the entire 28 volts is across the capacitor.
    I assume he derivation of the process is in your book and gives
    i = Io e^-t/(RC)
    From that compute i at t = 9
    then the voltage on the resistor is
    Vresistor = i R
    and
    Vcapacitor = 28 - Vresistor

  • Physics -

    Hey thsnks for your help, regarding the first question i found the capacitance to be 7.522e-7 F. Do i then use the formula Q=CV to work out voltage, if so how do i get Q? and how do i use the time of 9 seconds given to work out my final answer which in the textbook was 13.3V

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. 12th grade

    A certain parallel plate capacitor consists of two identical aluminium plates each of area 2times 10^-4 m^2.the plates are separated by a distance of 0,03mm, with air occupying the space between the plates. 1-CALCULATE THE CAPACITANCE …
  2. Physics

    A certain parallel capacitor consist of two identical aluminium plates, each of area 2times 10^-4m^2. the plates are separated by a distance of 0,03mm, with air occupying the space between the plates. CALCULATE THE CAPACITANCE OF THE …
  3. Physics

    A capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference between the plates and has charge Q1. If the separation …
  4. Physics

    A parallel-plate capacitor is constructed from two circular metal plates or radius R. The plates are separated by a distance of 1.2mm. 1. What radius must the plates have if the capacitance of this capacitor is 1.1 uF?
  5. Physics

    A parallel-plate capacitor is constructed from two circular metal plates or radius R. The plates are separated by a distance of 1.2mm. 1. What radius must the plates have if the capacitance of this capacitor is 1.1 uF?
  6. Physics

    A capacitor has two overlapping plates of width 4.9 m and length 3.5 m separated by 1.3 cm. A dielectric of dielectric constant ê = 58.0 fills the space between the plates. If this capacitor is connected to a 35 V battery, how much …
  7. physic's problem

    A square parallel plate capacitor in a circuit with a 2.0 V battery is replaced with a new one. If the sides of the new plates are 3 × as large as those of the old, and the distance between the plates is 1/4 of the distance between …
  8. Physics

    Consider the process of charging a parallel plate capacitor with circular plates of radius R=5 cm separated by a distance d=0.2 cm. At some time t1, the capacitor is being charged with a current I=0.04 A. Consider a point P on the …
  9. Physics

    Consider the process of charging a parallel plate capacitor with circular plates of radius R=5 cm separated by a distance d=0.2 cm. At some time t1, the capacitor is being charged with a current I=0.04 A. Consider a point P on the …
  10. Physics

    A parallel plate capacitor has a rectangular plates with length 5cm and width 3cm. They are separated by a distance 12m and hooked up to a 20V battery A.) what is the area of each plate in m^2 B.) assuming nothing else is present on …

More Similar Questions