voltage across resistor

Discussion in 'General Electronics Chat' started by anoopisaac, Oct 15, 2010.

  1. anoopisaac

    Thread Starter New Member

    Oct 15, 2010
    I am newbile to electronics,trying to learn fundamentals. I read that if resistor is present in a circuit , voltage drop across the resistor will be same as that of the battery.So in that case voltage drop between + end of the battery and resistor will be zero, so how come current flows ?

  2. steinar96

    Active Member

    Apr 18, 2009
    The battery creates energy from chemical reactions which it represents in the form of a positive voltage between it's terminals. When you connect a resistor across it the resistor dissipates this energy.

    If we start at the negative end of the battery and work our way up trough it to the positive terminal we will see that the voltage has increased by the battery voltage V. If we continue trough the resistor connected be end back up at the negative terminal and what we see is that the voltage has decreased across the resistor.

    Adding this mathematicly we have
    Vbattery + Vresistor.
    But seeing that VBattery = V
    and Vresistor = -V
    we get that moving trough the circuit "loop" the sum of the voltages is zero.
    This is what we call the kirchoff voltage law that states that the total sum of voltages trough a closed loop in a circuit adds to zero at all times.

    The point being that voltages have "polarity". And you should study kirchoffs voltage and current law to understand circuits better. These laws should be the starting point in your study of fundamental circuit analysis.