basic things about voltage and current.

[sundar]

what is relation between voltage and current and don't take resistance here.
if we supose say when there is increase in voltage whwt happens to current?is it decrease or increase?

 

[MikeMl]

It is fundamental that you specify the load across which the voltage is applied, and through which the current flows.

If the load is an Ohmic resistor, then current is linearly proportional to voltage.

If the load is non-linear (lamp, semiconductor diode, lots of other things), then the most you can say is that if the voltage increases, the current increases too.

If the load exhibits "negative resistance" (e.g. Tunnel diode), then an increase in applied voltage can produce a reduction in current (very special case).

 

[sundar]

thanks for your information.
i) current flows in a closed circuit....in domestic application we get 230v a.c. and amount of current is?
ii)is it right to say there is no current or there is no power ?answer me with a reason.

 

[bychon]

The amount of current available in a domestic circuit is the amount allowed by the circuit breakers in the building.
When there is no current flowing there is no power because the definition of power is current times voltage. zero times anything is zero.

 

[Gary B]

thanks for your information.
i) current flows in a closed circuit....in domestic application we get 230v a.c. and amount of current is?
ii)is it right to say there is no current or there is no power ?answer me with a reason.

Actually, it is correct to say either. Given a fixed circuit like a light bulb (bad example because of the way an incandescent light works but let us assume it works like most people think for this case) if you increase the voltage the current will also increase. If you lower the voltage, the current decreases. Power is voltage times current and energy is power times time. So depending upon the point you wish to make, you can talk about the presence or absence of voltage at a particular point, whether there is current flowing or not, if power is being dissipated or the total amount of energy expended.

 

[indulis]

... "negative resistance"...

Just like a SMPS.

 

[ericgibbs]

Just like a SMPS.

hi,
Some of the very early electric lamps used a carbon filament that had a negative temperature coefficient of resistance.
Tube Time Blog Archive Carbon Filament Light Bulb

There is currently research in to combining negative and positive resistance to produce a material with zero resistance, with carbon fibre use.

 

[Gary B]

That was positive and negative temperature coefficients, not positive and negative resistance. You still have to get close to absolute zero (well liquid air temperatures) to get a material to go into superconductivity.