Physics, 17.03.2020 17:13 howell62

A capacitor consists of two concentric cylinders. The inner cylinder has a radius of 0.001 m and the outer cylinder a radius of 0.0011 m. The length of the capacitor is 1 m. If centered on the z-axis, the region 0 < ∅ < π has a dielectric constant of 2 and the region π < ∅ < 2π a dielectric constant of 4. Find the capacitance. Ignore fringing fields.

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Answer from: jjjoooorrrrddddaannn

The capacitance is 1.75 nF

Explanation:

From the question we are given that

The inner radius is $r_{in} = 0.001$

The outer radius is $r_{out} = 0.0011 \ m$

Length of the capacitor is L = 1m

The dielectric constant is $Di = 2 \ for \ 0 < \phi < \pi$

The dielectric constant is $Di_2 = 4 \ for \ \pi < \phi < 2\pi$

Generally the capacitance of a capacitor can be mathematically represented as

$C = \frac{\pi \epsilon_0 Di_1 L}{ln\frac{r_{out}}{r_{in}} } + \frac{\pi \epsilon_0 Di_2L}{ln\frac{r_{out}}{r_{in}} }$

$= \frac{\pi \epsilon_0 L (Di_1 + Di_2)}{ln\frac{r_{out}}{r_{in}} }$

$= \frac{(3.142)(8.85*10^{-12})(1)(2+4)}{ln\frac{0.0011}{0.001} }$

$=1.75*10^{-9} F$

1.75nF

Answer from: Quest

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.

Answer from: Quest

most voltage drop calculators want the distance between the source and destination. then internally, they double it so both the source and return wires are calculated. but you need to know which distance the calculator uses so you're not half of what you should be or double what you should be.

most circuit breakers will not take a #6 directly, so the electrician will have to splice on a smaller pigtail. you also have to upsize the grounding wire when you upsized the ungrounded (hot) wire (see note in 250.122). this will preclude using most cable assemblies, as a cable with #6 copper will most likely only have a #10 grounding conductor. you need a #6 grounding conductor if the circuit is 20a. a #8 cable is no better, as it will have a #10 grounding conductor too. but most 20a breakers will take a #8 directly.

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