Dielectrics Interview Questions 

Product Description
RG6 - Coaxial Cable For CATV/CCTV/Satellite

Conductor: 1.02 Bare copper/ Copper Clad Steel
Dielectric: 4.57 mm Foam polyethylene
First Shield: Bonded AL/P
Second Shield: Aluminum wire braid 60% or 90% coverage
Jacket: 6.86 mm black PVC

Certification: UL
Flame Retardant (CM, CMX, CL2, CL2X, CATV, CATVX Type) &UV Resistant is available.

APPLICATION
Used as a distribution cable for indoor CATV, CCTV systems and as a connection cable for satellite systems where lower attenuation required.

A parallel-plate capacitor has dimensions 3.5cm ´ 5.2 cm. The plates are separated by a 1.1-mm thickness of paper (dielectric constant k = 3.7). What is the charge that can be stored on this capacitor, when connected to a 1.5-V battery? (e0 = 8.85 ´ 10-12 C2/N×m2)



HERE IS WHAT I DID......


C = (EoErA)/d

Eo = 8.85x10^-12 F/m

Er = 3.7

A = 18.2x10^-4 m^2

d = 1.1x10^-3 m


so,
C = {(8.85x10^-12)(3.7)(18.2x10^-4)}/(1.1x10... = 54.1781x10^-12 F

so, maximum charge is
Qmax = CVmax = (54.1781x10^-12)(16x10^3) = 866.85x10^-9= 867 nC


867 nC doesn't seem right. Where did I go wrong?

Okay, our water heater is under warranty with a well known major department store. The water heater stopped working completely (no hot water and was leaking). The store sends some plumbers out who charged over $600 dollars to install the water heater because they say the area for the heater needed to be brought up to code. Here is the cost for what they did:
Water Heater Installation for the department store1
Permit1
Thermal Exp Dev to meet code1
Dielectric unions 2 $50 each
Gate Valve1 $53
Gas Valve1 $53
Gas line1 $65
Vent pipe1 $65
custom water lines 2 $ 75 each
pressure reducing valve 1 $225

Now the only thing they did with the water lines was to leave them in tact and put on two small cooper pipes at the top of the water heater where the water lines attached. The vent leading into the ceiling they just left most of the old tin pipe and added a small tin pipe to it with screws. Looks shabby to me.

Design a 0.4 µF parallel-plate capacitor with air between the plates that can be charged to a maximum potential difference of 800 V.
The dielectric strength of the air is 3 × 10^6 V/m and the permittivity of free space is 8.85 × 10-12 C2/Nm2.
What is the minimum possible separation between the plates? Answer in units of mm.

What minimum area must the plates of the capacitor have? Answer in units of m2.

I am trying to calibrate a CS 616 reflectometer in a mature fine tailing material. The CS 616 is produced by Campbell Scientific and uses the difference in dielectric constant between water and the surrounding soil to determine the average moisture content of the soil. The link to the model is:

http://www.campbellsci.com/documents/lit...

The problem that I am having is that the CS 616 reading does not seem to change although the soil seems to be physically drying out. I have been drying the tailing material in an oven for hours on end however, the CS 616 reading stays nearly consistent.

Is EC of the tailing material affecting the reading? Is there any reason for why the CS 616 is not registering a change in moisture content?

Would a micrwave make a good electrolizer ? It can make water boil, right ? Could it be use to cause the hydrogen / oxygen separation everyone is looking for ? I understand the optimal temperature for an electrolisys separator is 150 degrees. But it can get hotter and still produce HHO, even more yet.
Everyone is looking for the HOLY GRAIL of the frequency at which the water now becomes a capacitor for its dielectric properties, and that at the overload threshold, what you get is a flow of hydrogen and oxygen.
It's like being on the burn-out edge of a regular capacitor, and keeping it there, on purpose. To get a boiling effect. Water separating will not be a negative as it is what we are looking for, but as in a capacitor, it would be the point off failure. Water does not fail, it gives-up.

Ok im getting closer I can feel it, I have been testing alot of wires and I did find a problem with the wiring harness connection some kind of black dielectric gel many years old and kinda dried up it wasn't making good contact I finaly have power to the fuse panel but there is still no power to the brand new fuel pump where the wires connect to the pump. I do have power to the sending unit but not to the pump I did pull the wires all the way back to the fuse panel connection and there where no cuts or anything. I did do a continuity test on the wires and they all checked out ok from the fuse panel to the pump the fuel pump relay is new and the 20 amp fuel pump fuse is also new so I really dont know where to go from here.

Parallel Plate Capacitor True or False
--------------------------------------...
I keep getting the questions wrong. What's not right?

Which statements are correct/incorrect for two oppositely charged, isolated parallel plates (Isolated means that the charge stays constant ):
(C=capacitance, U=stored energy, +Q and -Q = charge on the plates).


1. When the distance is doubled, U increases. T
2. Inserting a dielectric decreases U. F
3. Increasing the distance, decreases the E field. F
4. When the distance is halved, Q stays the same. F
5. Inserting a dielectric increases C. T
6. Inserting a dielectric increases Q. T
7. When the distance is doubled, C increases. F

Three square metal plates A, B, and C, each 12.0 cm on a side are arranged as on the figure. The plates are separated by sheets of paper 0.45 mm thick and with dielectric constant K=4.2. The outer plates are connected together and connected
to point b. The inner plate is connected to point a. i) Copy the diagram and show by plus and minus signs the charge distribution on the plates when point a is maintained at a positive potential relative to point b. ii) What is the capacitance between points a and b? iii) What is the energy stored in system if point a is kept at +120 V with respect to point b?

Consider a charged water droplet of radius R and charge Q uniformly distributed over its surface. From energy considerations, obtain an expression for the minimum charge that permits the droplet to spontaneously split into (i) two droplets of equal size, (ii) three droplets of equal size. Show that both the processes are energetical ly allowed for a droplet of charge Q = 5 x 10^(-10) C and radius R = 1 mm. Will these processes actually occur if the dielectric breakdown of the surrounding medium takes place at a field strength of 3 x 10^6 Vm-1 ?




could you please post the detailed soln

I have a 1994 Caravan, 3.0l V6 3 speed automatic A/C No Cruse control. and for a while during humid/rain days my Speedometer would cut out, causing the van too go into Limp-home-mode and the check engine light would also go on. Turning the car on/off waiting a while and the problem would fix its self, until recently were it has cut out and not come back. the computer gave me code 12 and 15 12 is the battery disconnected message, and code 15 says the speed sensor. So I went too the junk yard, and tried 2 different speed sensors hoping too fix the problem, but no luck, and no speed sensor. At one point I had too replace the Body control module, and the temperature gage has never worked since I replaced it... I have tried opening every plug under the hood i could get my hands on, spraying them with contract cleaner and putting dielectric grease and reseting the connections, still with no luck.
what else might I be missing ?

for the sake of simplicity we often call a dielectric as an insulator.Both do not have mobile charged particles.still the terms cannot be used as such.kindly answer my query.

1. Calculate the capacitance per unit length (in nF/m) of an axon whose radius in 5.0 µm. The membrane acts as an insulator between the conducting fluids inside and outside the neuron. The membrane is 5.8 nm thick and has a dielectric constant of 7.0.

2. The potential difference across a cell membrane from outside to inside is initially at –90 mV (the resting potential). When a stimulus is applied, Na+ ions are allowed to move into the cell so that the potential changes to +18 mV for a short period of time. If the membrane capacitance is 1.0 µF/cm^2, how much charge (in nC) moves through a membrane of area 0.05 cm^2?
**1,080,000 nC

3. The immediate cause of many deaths is ventricular fibrillation, an uncoordinated quivering of the heart as opposed to rhythmic and steady beating. An electric current passing through the chest can cause momentary paralysis of the heart muscle, after which the heart will sometimes restart its organized beating. Assume that an energy of 350 J paralysis of the heart muscle, after which the heart will sometimes restart its organized beating. Assume that an energy of 350 J is to be delivered to the chest from a defibrillator having a 30 µF capacitance. To what potential difference (in V) must the defibrillator be charged?

I've got a 2000 Suzuki Esteem, wih no manual. A few weeks ago, the old battery went dead out of the blue. When I turned the ignition, nothing happened, It didn't turn over, ir even click. After we get a jump, it idles just fine until I take the parking brake off and the daytime running lights turn on.

The store said the battery was fully charged, but the cells were bad, so I got a new one, but the same problem happened with that a few times.

Dad says the new battery might not have been fully charged, or maybe there was a loose connection, or maybe a short. Well, we charged the battery as much as we could, and I got the connections all cleaned and coated in dielectric grease, but I don't believe that's the problem.

Whenever I put the key in, I've always gotten a little shock, so I'm pretty sure there's a short somewhere. I'd like to know how I can find it.

Hey Guys i have tried to attempt some of these questions i just dont understand where to start from i need the main formulas that can help me do these questions thanks alot

a) coaxial line consists of an inner conductor of radius RA = 1 cm
and outer conductor with an internal radius of RB = 10cm. The
internal conductor is charged positively with a linear charge density
of ?l = +100 nC/m. Calculate the potential difference between RA
and RB.


(ii) Find the total effective capacitance of the coaxial line described in
(i) if the length of the line is 30 cm and the region between the
conductors is filled with dielectric with relative permittivity of 2.5.


(e) A coaxial line consisting of inner and outer conductors with unknown
radii is located in zero gravity conditions and has a potential difference of
8 kV between electrodes. A particle with a charge of +1 mC and with a
mass of 40 g is located almost on the surface of the central, positively
charged electrode.

The particle is released from its location with zero velocity initially and
starts to move towards the opposite electrode. Calculate the velocity
which the particle will have when it reaches the opposite electrode.