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A few Questions from electricity, em waves, kinematics

Riya Posted:

1) A particle moves along a straight line parallel to the x-axis at a constant velocity, Its angular momentum about the origin?

2) Can a free electron moves from higher potential to low potential?

3) Progressive wave carries energy in a plane perpendicular to the plane wave front-is the statement true?

4) Why a heavier body doesn’t fall more quickly than a lighter body?

5) Is it possible to transfer electic charge from a body of a lower potential to a higher potential?

Numerical Problem from Capacitance

Nishant asks:

Capacitance“In the diagram, what is the potential difference between A and B? Please explain the procedure.”


(Due to the large number of questions I am receiving per day, I am posting the question first and I will answer them later. Visitors, please feel free to respond to the answered and unanswered questions.)

Charge on Earth

Udit SIngh Asks:

“Does earth get charged? if it’s then where these
charge goes.”

Answer: The net charge of earth as a whole (including the atmosphere) is approximately zero. But the surface of earth(the solid part) has a net negative charge and the air blanket surrounding it has almost equal amount of positive charge. Due to this there exists an average electric field of 100 V/m near Earth’s surface.

The charge on earth is distributed on its surface only.

Please refer to the following links for further information.

There are some associated questions expected in relation to these. I hope that the readers will ask those in response to this post as comments so that the discussion can go on.

Conventional Current and Real Current

Manishankar Asks:

“What is the difference between conventional current and real current?”



Conventionally. the direction of current is defined as the direction of flow of positive charges. But in real case, the flowing charges are not positive (in the case of a metal); but the current carriers are electrons which are negatively charged. So, the real current is (the word current means flow) in a direction opposite to the conventional current.

So, if you are asked to find the direction of current in  a circuit, you have to find the direction which is opposite to the direction of flow of electrons.

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?


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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February 2021

Schrodinger’s Cat in Daily Life

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