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## Reaction problem

NINE FIVE RUPEE COINS ARE PUT ON TOP OF EACH OTHER ON A TABLE.EACH COIN HAS A MASS m kg .THE REACTION OF THE FIFTH COIN(COUNTED FROM BOTTOM)ON SIXTH COIN IS.
4mg as there are invited4 coins above the 5th coin from bottom.

## What is pseudo force

What is pseudo force when it is applied ?

Pseudo force is also called fictitious force.

A fictitious force arises when a frame of reference is accelerating compared to a non-accelerating frame.

For example if you consider a person standing at a bus stop watching an accelerating car, he infers that a force is exerted on the car and it is accelerating. Here there is no problem and the pseudoforce concept is not required

But, if the person inside the accelerating car is looking at the person standing at the bus stop, he finds (more…)

## WORKING OF A TRANSFORMER

Sir,im not understanding how transformer works?while current is going from one station to other we keep high voltage and very less current to decrease power loss but current is proportional to voltage how can u make low current using high voltage?

A transformer works on the principle of mutual induction. [mutual induction is the phenomenon of production of emf in a coil due to the change in the strength of current through a neighbouring coil] Transformers are of two kinds – step up and step down.

A step up transformer converts low voltage (high current) ac to high voltage (low current) ac.

In the case of an ideal transformer, there is no power loss.

In that case,

input power = out power

Vin Iin = Vout Iout

[This equation shows how an increase in output voltage results in a decrease in out put current]

Long distance transmission of ac requires low  current as the heat dissipated during transmission is proportional to the square of current.

If we use a step-up transformer , it steps up the voltage and consequently steps down the current so that VI is the same.

In the case of real transformers, there are some power losses within the transformner, however, an increase in output current through mutual induction will essentially result in a decrease in output current.

Hope that the matter is clear now. In case of doubt, please post them as comments to this post.

## A question from Potentiometer (asked in Board Exam)

For the potentiometer circuit shown in the given figure, points X and Y represent the two terminals of an unknown emf E’. A student observed that when the jockey in moved from the end A to the end B of the potentiometer wire, the deflection in the galvanometer remains in the same direction. What may be the two possible faults in the circuit that could result in this
obsevation ?
If the galvanometer deflection at the end B is (i) more, (ii) less, than that at the end A, which of the two faults, listed above, would be there in the circuit ?

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