Flow of electrons and direction of current
We say current flow opposite to electron flow but what is current?
Sid asked
Answer:
Electric current is defined as the rate of flow of charges, ie; the amount of charges flowing in 1 sec.
The direction of current was conventionally defined as the direction of flow of positive charges.
In a metallic conductor, the negatively charged particles (electrons) are moving and therefore the direction of current is taken as opposite to the direction of flow of electrons.
Hope the concept is clear.
Categories: Ask Physics, Current Electricity, Interesting Questions Tags: charge, current, electricity, electron
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
Categories: Ask Physics, Electrostatics Tags: capacitance, charge, electricity, electrostatics, pd, potential, potential difference
Doubts from Faraday’s Experiments on electromagnetic induction
I wanna ask that in faradays’s first experiment with coil and magnet,when the magnet is moved away from coil the deflection in galvanometer becomes opposite as compared to first case…..what leads to this and if that means direction of current becomes opposite so HOW and WHY the direction of this changes…..plz can you tell me the practical reason of this…..its really confusing me!!!
Asked Arti
Answer will be posted soon
(Visitors are welcome to post their response via comments)
Categories: Ask Physics, Electromagnetism Tags: ask Physics, electric, electricity, electromagnetic induction, EMI, physics, problem
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?
Asked Avinah Boinepalle
Answer:
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.
