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Capacitance, voltage and Potential difference

the capacity of parallel plate condenser is 5 micro Faraday. When a glass plate is placed between the plates of the conductor  its potential become 1/8th of the original value. The value of dielectric constant will be
(A)1.6
(B)5
(C)8
(D)40

 

Answer:

The charge remains same

Use Cm=KCo
and
V reduced to 1/8 means capacitance increased 8 times since Q=CV
So, the answer is evident

How does a battery create potential difference?

How battery creates potential difference??? …plz give me a detailed description of it.

Posted by Arti.

Answer:

Potential difference means “Difference in electrical potential. In an electrochemical cell, the potential difference is created by chemical reactions. In a cell there are two electrodes and they are maintained at different potentials by the chemical reactions taking place.

Please refer to the following links for more information.

Potential Difference

Pawan Asked

“What is meant by potential difference?”

Answer:

“Potential Difference between two points is the difference in Potential between the two points and is equal to the work done per unit charge ion carrying a positive test charge from one point to another against the electric field and without any acceleration”

Differences Between EMF and Potential Difference

What is main relationship between EMF and potiential difference?

Answer: The question is already answered at http://askphysics.com/difference-between-emf-and-pd/

Is ohm’s law universally applicable?

Amritha asked:

“Is ohm’s law universally applicable?”

Answer:

The Ohm’s law states that “The current through a conductor is directly proportional to the potential difference applied across its ends provided the physical conditions such as temperature remains the same

From the statement it is implied that it is not a universal law, and is applicable to conductors. It is not valid for semiconductors and electronic devices.

The substances which obey Ohm’s law are said to be ohmic and those which do not obey Ohm’s law are “Non Ohmic

Difference between emf and pd

ananthesh asked:

“can you please explain about emf and PD of a cell?”

Answer:

EMF stands for electromotive force.

EMF of a cell is equal to the potential difference between the two terminals of a cell when no current is drawn from it.

Pd (potential difference) between any two points on a circuit is defined as the work done per unit charge in carrying a positive test charge from one point to the other. With reference to a cell, the potential difference between the terminals of a cell when a current is drawn from it is called terminal voltage.

Fluorescent lamp flickers and incandescent lamp does not!

Swathi asked:

Why do fluorescent lights flicker (tube lights) while Incandescent bulbs don’t , especially when they are switched on..Is it an effect of the pulses as sensed by the retina?

Ans:

If your question is regarding the start up flickering,

the fluorescent lamp requires a very high voltage to start conducting. In a lit up tube light, the conduction is taking place through the gas filled inside the tube. As you know, air is a bad conductor. To make it conducting, it is to be ionized first. This is done by developing a very high potential difference between the two ends of the tube by the combined action of starter and the choke. Starter is a make and break arrangement which makes the supply intermittent. When the supply is disturbed, a huge potential difference is developed and flashes produced inside the tube ionizes the gas inside the tube. After such a few occurrences, the gas will be ionized enough to make the gas conducting. During this process lot of UV radiations are emitted. This strikes the fluorescent coating on the tube which converts UV radiations to visible light. So, the tube light flickers due to the action of starter during the startup time.

But, if your question is with regard to the flickering of a lit up fluorescent lamp, …………. 

I will answer it later

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