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# Tag Archives: Voltage

## Transformers

Please explain what is transformer and tell what is the reason behind the working of transformer that it reduces potenial when current is high and increases potential when current is low?

Explain widely and deeply with concepts.

Answer:

Transformer is a device based on mutual inductance and is used to change the voltage of alternating (or varying) current. There are two types of transformers – stepup and stepdown.

A step-up transformer increases the voltage as the step-down transformer decreases the ac voltage.

When a transformer changes the alternating voltage, it is not adding any **power**, it only transforms the voltage.

As power is the product of voltage and current, as voltage increases, the current decreases. (and vice versa)

The following links will help you understand transformers in great detail.

- http://www.physlink.com/education/askexperts/ae427.cfm
- http://en.wikipedia.org/wiki/Transformer
- http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/transf.html
- http://www.nuffieldfoundation.org/practical-physics/explaining-how-transformer-works

## V proportional to I or I proportional to V in Ohm’s Law?

Why we used I proportional to V?

Can we write V proportional to I also?

Answer:

Both are ok. If we are changing the current and observing the voltage, then it is V∝ I

If we are changing the voltage and observing the current, then

I∝ V

In general, we write

**the dependent variable proportional to the independent variable**

dependent variable = the quantity measured by us

independent variable = the quantity fixed by us

## A Numerical problem from electricity

In the given diagram,the cell and the ammeter, both have negligible resistance. the resisitors are identical. With switch K open , the ammeter reads 0.6 A. What will be the ammeter reading when the switch is closed?

-Mohit asked

Answer:

When the switch is open, the effective resistance is R/2, since the two resistances R each are in parallel.

Therefore, the pd, V = I x R/2 = 0.6 x R/2 = 0.3 R

When the key is closed, the effective resistance becomes R/3

Now the reading of the ammeter, I’ = V/(R/3) = 0.3R/(R/3)=**0.9A**

## Work done in accelerating a proton

The mass of a proton is 1840 times that of an electron. it is accelerated to a potential difference of 1kV. find the amount of work done in process. (Ujjwal Sharma asked)

**Answer**

The work done = the KE acquired = eV=1.6 x 10^{-19} x 1000 = 1.6 x 10^{-16 }J

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## Difference between Dielectric Break Down and Corona Discharge

HOW IS CORONA DISCHARGE DIFFERENT FROM DIELECTRIC BREAKDOWN IN THE CASE OF VANDEGRAFF GENERATOR

Asked Deepika

###### The important points referring to answer are already hyperlinked here.

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