Capacitance Flashcards
(7 cards)
Explain what is meant by dialetric constant of 6.0
The dialetric constant is permettivity of medium/permittivity of free space and is equal to 6
Mica is made up if polar molecules. As the mica is inserted between the plates, the capacitance of the capacitor changes.
Explain how the polar molecules cause this change in capacitance.
Polar molecules align with their positive side facing the negative plate producing a counter electric field. The potential difference reduces between the capacitor plates but charge remains the same so capacitance (Q/V) increases.
In one situation, the variable capacitor is too large for the available space.
The same maximum capacitance is required using plates that have half the diameter of the original capacitor.
Explain with numerical detail two ways in which this can be achieved.
Insert dialetric between plates with permittivity=4
Reduce air gap by 1/4
How does the capacitance of a capacitor change if the distance between the plates is halved, and the area of the plates is doubled?
The capacitance of a parallel plate capacitor is directly proportional to the area of the plates and inversely proportional to the distance between them. If the distance between the plates is halved and the area of the plates is doubled, the capacitance will increase by a factor of four. This is because the increase in plate area has a greater effect on capacitance than the decrease in plate separation.
What is the time constant of an RC circuit?
The time constant of an RC circuit is a measure of how quickly the capacitor charges or discharges in response to a change in voltage. It is given by the product of the resistance and capacitance in the circuit, and is usually given the symbol τ. The time constant represents the time it takes for the capacitor to charge or discharge to approximately 63% of its final voltage.
What is the effect of adding a dielectric material to a capacitor?
Adding a dielectric material to a capacitor increases its capacitance. This is because the dielectric material reduces the electric field between the plates, allowing for more charge to be stored on the plates for a given potential difference. The amount by which the capacitance increases depends on the dielectric constant of the material, which is a measure of its ability to store electric charge.
What is capacitance?
Capacitance is the ability of a capacitor to store electric charge. It is defined as the ratio of the charge stored on each plate to the potential difference between the plates, and is usually given the symbol C. The unit of capacitance is the farad (F).
