Confusion with Resistance and Current

In summary: JIn summary, for a capacitor discharging with a resistor attached, the discharge time is directly proportional to the resistance. This can be calculated using the time constant, RC. The voltage and charge on the capacitor are directly related and the voltage is affected by distance, plate area, and permittivity, as well as the charge on the plates.
  • #1
AsksQuestions
2
0

Homework Statement


This is my question not from homework or anything.
If a capacitor has stored a charge in a circuit and is discharging, and a resistor is attached to this circuit, what affect does this have on the discharge time?
If the resistor makes it harder for a current to flow, does this mean the current takes longer to be used up?
Also I can't differentiate between charge and voltage in a capacitor.

Homework Equations


V=IR
C= Q/V
Q=It


Any help please and thanks, detailed as.
 
Physics news on Phys.org
  • #2
You are completely correct about the capacitor current. For a resistor connected across a charged capacitor, the current as a function of time is an exponential decay: I = V/R*e^(-t/(RC)). The product RC is the time to fall to 63% of the initial value. RC is called the "time constant"
http://en.wikipedia.org/wiki/Time_constant

The charge and potential on the capacitor are directly related by one of your formulas, Q = C*V. As the charge increases, so does the voltage.
 
  • #3
AsksQuestions said:

Homework Statement


This is my question not from homework or anything.
If a capacitor has stored a charge in a circuit and is discharging, and a resistor is attached to this circuit, what affect does this have on the discharge time?
The time required to discharge to 1/e of its original charge is t=RC seconds. So as the resistance increases, the discharge time increases proportionately.
If the resistor makes it harder for a current to flow, does this mean the current takes longer to be used up?
Yes. See above.
Also I can't differentiate between charge and voltage in a capacitor.
The voltage between the capacitor plates depends on the distance between the plates, the plate area and permittivity of the material between the plates as well as the charge on the plates.

AM
 

1. What is the difference between resistance and current?

Resistance is a measure of how difficult it is for electricity to flow through a material, while current is the rate at which electricity flows through a circuit. Resistance is measured in ohms (Ω), while current is measured in amperes (A).

2. How are resistance and current related?

Resistance and current are inversely related - as resistance increases, current decreases, and vice versa. This relationship is described by Ohm's law, which states that current (I) is equal to voltage (V) divided by resistance (R), or I = V/R.

3. Can resistance and current be measured directly?

Resistance can be measured directly using a multimeter, while current is usually measured indirectly by using a multimeter to measure the voltage across a known resistance and then using Ohm's law to calculate the current.

4. How does temperature affect resistance and current?

For most materials, as temperature increases, so does resistance. This means that as temperature increases, current decreases. However, there are some materials, such as semiconductors, that have the opposite effect - their resistance decreases as temperature increases.

5. What factors can affect resistance and current?

Resistance is affected by the type of material, the length and thickness of the material, and the temperature. Current is affected by the voltage applied to the circuit, the resistance of the circuit, and the type of material used for the conductor.

Similar threads

  • Introductory Physics Homework Help
Replies
4
Views
689
  • Introductory Physics Homework Help
Replies
3
Views
508
  • Introductory Physics Homework Help
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
13
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
503
  • Introductory Physics Homework Help
Replies
1
Views
889
  • Introductory Physics Homework Help
Replies
4
Views
208
  • Introductory Physics Homework Help
Replies
14
Views
558
  • Introductory Physics Homework Help
Replies
3
Views
194
  • Introductory Physics Homework Help
Replies
1
Views
2K
Back
Top