Are voltage and current interdependent?

Replies

• 

  Kaustubh Katdare

  Gayathiri pillai

  in my class i got a doubt about relationship between voltage and current.why they are so important?

  They are related by an equation : V = IR where V is 'voltage difference between two points', R is the resistence between those two points and R is the resistance officered to the current between the two points. It's also called as 'Ohm's Law'.
  
  Could you tell us the doubt you had in your class about the relation between voltage difference and current?
• 

  Ramani Aswath

  If you have a voltage source with zero internal resistance, you can have any current from zero (open circuit) to infinity (short circuit). In that sense there is no dependence.
  However, in any given real circuit what #-Link-Snipped-# says applies.
• 

  arunchary

  because of the following features
  
  Voltage is a measure of the energy carried by the charge.
  Strictly: voltage is the "energy per unit charge".
  
  

  • The proper name for voltage is potential difference or p.d. for short, but this term is rarely used in electronics.
  • Voltage is supplied by the battery (or power supply).
  • Voltage is used up in components, but not in wires.
  • We say voltage across a component.

  
  

  • Current is the rate of flow of charge.
  • Current is not used up, what flows into a component must flow out.
  • We say current through a component.
  • Current is measured in amps (amperes), A.
  • Current is measured with an ammeter, connected in series.
    To connect in series you must break the circuit and put the ammeter acoss the gap, as shown in the diagram.
• 

  arunchary

  please follow the diagrams on dropbox.
  #-Link-Snipped-#
• 

  simplycoder

  I don't know whether this post is applicable for the above question.
  Voltage and Current are also dependent on the frequency.
  
  So By Ohm's law, as V increases, I would also increase where R>0,
  However this is not applicable at RF. In this case, as V increases, I would decrease and vice versa.
  
  basically V and I follow linear relation in all frequencies below RF, and at RF and above they follow differential relationship.
  
  
  None of the electrical laws are applicable when the application frequency is at or above RF(Radio frequency).
• 

  Jeffrey Arulraj

  AC Resistance of any material is larger than its corresponding DC resistance.
  
  That is the reason why 10V DC and 10V AC supply produce different currents in the same conductor due to different resistance.
  
  For conductors in DC only the resistances play a vital role and reactances due to capacitive and inductive are either open or short circuited giving you comparatively lesser impedance
  
  But in AC all three elements are significant and has higher resistances Making them to conduct lesser
  
  In RF as #-Link-Snipped-# says the effect of the capacitive and inductive components are peaked and so they seem to show inverse ohmic conditions But that is not true.
  
  V is proportional to I for constant R only. Since this R varies dynamically in AC supply there seems to be a decrease in current as higher voltages are applied
• 

  simplycoder

  I was referring to constant load.
  This can be referred,
  RF & Microwave Design Essentials: Engineering Design and Analysis from DC to ... - Matthew M. Radmanesh - Google Books
  
  My emphasis was more on the linear vs differential relationship. which is not true in case of low frequencies.
• 

  Gayathiri pillai

  The_Big_K

  They are related by an equation : V = IR where V is 'voltage difference between two points', R is the resistence between those two points and R is the resistance officered to the current between the two points. It's also called as 'Ohm's Law'.
  
  Could you tell us the doubt you had in your class about the relation between voltage difference and current?

  certainly sir.iam a first year eee student.when my faculty explained about currrent and voltage,she said current flows because of potential difference.in this case iam deeply intruged that why it is so.if it is not will the current will not flow.please tell me why it is.thank u for above explanation sir.
• 

  arunchary

  hi watch this videos and texts in following links
  
  
  #-Link-Snipped-#
  #-Link-Snipped-#
• 

  simplycoder

  Gayathiri pillai

  certainly sir.iam a first year eee student.when my faculty explained about currrent and voltage,she said current flows because of potential difference.in this case iam deeply intruged that why it is so.if it is not will the current will not flow.please tell me why it is.thank u for above explanation sir.

  On a higher level of abstraction, do not consider voltage and current as two different entities, One can also frame the same question in different way. - Does current flow because there is potential difference or since there is potential difference, the current flows from higher potential to lower.
  
  You can think of water jar fully filled.
  Now make two holes in it, one in middle and one lower than that.
  
  You can see that water flows out through both holes, this flowing water can be related to current.
  
  Also make a note that water flowing through lower hole would be with greater force than that of the middle one. This resembles the same concept of higher the potential difference, greater is the current.
  
  Now consider that water level has decreased from top and has come to middle, when this will happen, you can see that water wont flow through the middle hole. This can be related to a special condition where no current flows when there is zero potential difference.
  
  The examples I gave you based on the equations of energy.
  Potential energy (PE)=mgh (mass * gravity * height from reference.)
  Kinetic energy (KE)=0.5mv^2.
• 

  lal

  Every conductor has free electrons. And you sure know current is the flow of electrons. If these free electrons could simply flow just by their own, we would have had infinite current.But that is not the Case.
  
  For these free electrons to move, we need a driving force. Now that is voltage. When voltage is applied across a conductor, the free electrons in it are forced to move. If the magnitude of voltage is increased, more electrons are forced to move. That is more current. Some how current seems to be directly proportional to voltage under normal conditions (ignore shortcircuit and opencircuit conditions for the time being). So clearly current flows because of the existance of a voltage (better said as potential difference).
• 

  Gayathiri pillai

  simplycoder

  On a higher level of abstraction, do not consider voltage and current as two different entities, One can also frame the same question in different way. - Does current flow because there is potential difference or since there is potential difference, the current flows from higher potential to lower.
  
  You can think of water jar fully filled.
  Now make two holes in it, one in middle and one lower than that.
  
  You can see that water flows out through both holes, this flowing water can be related to current.
  
  Also make a note that water flowing through lower hole would be with greater force than that of the middle one. This resembles the same concept of higher the potential difference, greater is the current.
  
  Now consider that water level has decreased from top and has come to middle, when this will happen, you can see that water wont flow through the middle hole. This can be related to a special condition where no current flows when there is zero potential difference.
  
  The examples I gave you based on the equations of energy.
  Potential energy (PE)=mgh (mass * gravity * height from reference.)
  Kinetic energy (KE)=0.5mv^2.

  thank you sir.now i can clearly understand.
• 

  simplycoder

  Gayathiri pillai

  thank you sir.now i can clearly understand.

  I am glad this helped you.