question on electric potential

Discussion in 'General Electronics Chat' started by electron_prince, Sep 19, 2012.

  1. electron_prince

    Thread Starter Active Member

    Sep 19, 2012
    I am trying to simplify the electronics fundamentals. Maybe they are easy for you but they aren't easy for me.

    so circuit theory is based on two basic laws.
    1. law of conservation of energy
    2. law of conservation of charge

    Electric potential at any point is defined as the amount of work required to bring a unit positive charge from infinity to that point.

    but the word "infinity" doesn't make sense to me. So I'll take electric potential as a relative quantity. Just as length we need to choose a reference point in order to define potential.

    now potential = energy/charge = work/charge

    In a circuit where resistors are connected in series with a voltage source (a battery, i'll take the negative terminal as a reference) , potential drops on every resistor. which mean that energy/charge also decrease. so why current which is rate of flow of charge remain the same?

    energy is dissipated across resistor in the form of heat. according to law of conservation of energy, the energy is decreasing. according of law of conservation of charge, electrons can't be destroyed. So electrons should slow down which in turn should decrease current.
    Last edited: Sep 19, 2012
  2. MrChips


    Oct 2, 2009
    If the voltage source were a fixed source of energy, such as a capacitor, the current would decrease (exponentially) over time.

    A voltage source such as a battery is a chemical reaction which keeps producing more energy.
    electron_prince likes this.
  3. electron_prince

    Thread Starter Active Member

    Sep 19, 2012
    wow, that was a great answer. Thank You.

    i was considering another answer.I was thinking that the voltage source first calculate the obstacles in its path and then release the electrons with an appropriate flow rate.
    Last edited: Sep 19, 2012
  4. crutschow


    Mar 14, 2008
    The voltage source simply applies a potential to the electrons. The electrons then flow at a rate as determined by the resistance in the path between the positive and negative terminals of the source.

    It's a simple analogy but thinking about current as water flow can help visualize the process. A pump generates the pressure (voltage) and any valves (resistance) in the line restrict the flow. The amount of water (electrons) does not change as it flows through the circuit although the energy (pressure/voltage) decreases as it flows through the restrictions.