## Why Rainbow is in the form of an arc?

Why is a rainbow always bent in the shape of a semi circle…?? but according to the theory light travels straight….!!! (Ramesh asked)

## Where is electricity stored after it is generated but before it is supplied? (Chat Transcript from FaceBook)

###### Where is electricity stored after it is generated but before it is supplied?
• Mahesh Sable Electrical power cannot be stored and,therefore,power plants must produce power as and when demanded.power stations r connected in parallel hence load is equally distributed,electric Power can be adjusted with help of step up or step down transformers.

• Mathew Abraham Transformer does not increase power

• Chitraja Rajan The demand for electricity varies randomly within a day itself…so there should be something which should be adjusted according to the demand.

• Vishnu Mohan G huge capacitors? i think i read somewhere like this.

• Rajat Sharma

Hi All, the question is very smart, i think electricity stored before generation is stored in Water(DAM), Uranium Rods(Nuclear), HydroCarbons(Coal, GAS). Electricity can only store when it is in Direct Current format like in Batteries, Capacitor(its a very small time to store/release) Well there are many source where we can store electricity. When electricity is in demand then Power generation takes place within huge Alternators, this powers generation takes places in terms of Phase Shift between all the power Houses across the country, if this phase shift is disturb then power grid fails. after this the transformers come into picture so as to reduce Resistance loses.

•

• Kannan Kannan Ps in my little knowledge electricity unable to store continuing process of generater get current
>________________________________

• Chitraja Rajan at the generation side electricity is high ac current ..if it is converted into dc then there should be large containers to store them and also need suitable convertors to convert it in either form every time

• Mathew Abraham In modern generators, there are equipment to control the rate of flow of water and in turn rate of rotation as well as the power generated. SO, it is quite right to say that electricity is generated as and when required. When you switch on a device power generation also increases until it reaches maximum capacity. Thereafter we will get less power. Remember the low voltage we suffer during the evening when the power consumption is maximum a few seconds ago · Like

## How to prepare for IIT JEE?

Surya Kant Dwivedi asks: “I am always confused in Physics that how can i do my best in Physics. It is my weakest portion in ’PCM’. Please guide me.

Excelling in Physics in IIT JEE requires systematic planned preparation. The first step is to make sure that you can solve all the exercises from NCERT text book (including the solved examples and additional exercises) confidently and completely. This ensures that you have sufficient exposure and you are up to the standard expected of you.

The next step is to get a good collection of questions asked previously in IIT JEE and solve them. If you are not able to solve a problem, you are welcome to post it here.

Recommended Books:

Fundamentals of Physics (Resnick Hallidey)

Concepts of Physics (HC Verma)

Irodov Problem in Physics

## Dimensions of angle, specific heat, heat, latent heat, frequency, charge, potential difference, resistance.

What are the dimensions of angle,specific heat,heat,latent heat,frequency,charge,potential difference,resistance?

• Angle does not have any dimension as it is a pure ratio
• Dimensions of Specific heat  = [M0L2T-2K-1]
• Heat has the same dimensional formula as that of energy [ML2T-2]
• Latent heat is the heat energy required to convert unit mass of a substance from one state to another without change in temperature. Therefore, the dimensions are [M0L2T-2]
• Dimensions of frequency = [M0L0T-1]
• Dimensions of charge = [AT]
• Dimensions of potential difference = [ML2T-3A-1]
• Dimensions of [ML2T-3A-2]

## A problem from light for class X

Sudhanshu Misra posted:

“An object is placed at a distance of 10cm from convex mirror of focal length15cm; find the position and nature of image?”

Ans:

f= 15 cm

u=-10 cm

v=?

substitute the values in the relation

$\frac{1}{f}=\frac{1}{v}+\frac{1}{u}$

and get the value of v as 6 cm

The image is virtual, erect and diminished

## Why we can’t see the stars, towards the horizon?

“i want to know, why we can’t see the stars, towards the horizon?
but we can see stars towards the zenith?

Ans:

Such an observation occurs at twilight. The main culprit here is the comparative greater distance of horizon as compared to zenith.

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