2
$\begingroup$
  1. I would like to think that voltage is like the force provided by the battery to move. When electrons are near the negative terminal of a battery, they experience a repulsive force which makes them move across wire; once they are in the vicinity of positive terminal, they experience an attractive force once they reach positive terminal. The electrons would stop moving if not for the energy produced in chemical reaction inside the battery (EMF),they are pushed near the negative terminal by this energy, which causes them again to go around and seek for positive terminal.
  1. Voltage is the energy given per unit charge; this causes them to move across the circuit and lose the energy while moving through resistor, which is taken as the voltage drop across that resistor.

Is my understanding right? If so, which of these are right? While studying Kirchhoff's Voltage Law, I came to know that it is a result of conservation of energy. Can anyone explain in terms of these two definitions? Finally, is voltage a force-like quantity or an energy-like quantity?

$\endgroup$

2 Answers 2

2
$\begingroup$

(a) Voltage is an energy-like quantity. It is the energy transferred per unit charge passing.

(b) "Voltage is the energy given per unit charge". This voltage is (misleadingly) called electromotive force (emf) if the energy is transferred from some form other than electrical potential. In a battery, chemical reactions at the electrodes provide an emf when there is a current.

(c) The emf causes a redistribution of charge in the circuit. Roughly speaking, as you imply, the negative terminal of the battery acquires a negative charge due to an excess of electrons, and the positive terminal gets a positive charge owing to a deficit of electrons. [In fact when the circuit is complete the surface charge distribution is more complicated than this, and depends on the resistances of circuit components.] These quasi-static charges set up an electric field that drives charge through the external circuit, rather as you have described in your (1).

As charge flows in the external circuit due to the electric field it loses electrical potential energy. (The energy is transferred to other forms, including heat.) We call the energy transferred per unit charge from electrical potential energy, potential drop. This can also be called 'voltage'.

(d) Because energy is conserved the energy given per unit charge passing through the battery equal to the energy per unit charge transferred to other forms, so the emf (or sum of emfs) is equal to the potential drop (or the sum of drops). This is one form of Kirchhoff's voltage law.

(e) Of course as charge goes through the battery it picks up an equal amount of electrical PE to that lost in the external circuit. (Here I'm neglecting internal resistance, but it can easily be catered for.) In other words the electric field set up by the (quasi-static) charge redistribution is a conservative field, and there is no change in potential energy over a complete cycle around the circuit. And we talk about the potential difference between the battery terminals.

$\endgroup$
0
$\begingroup$

Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points, which (in a static electric field) is defined as the work needed per unit of charge to move a test charge between the two points.

Hence Voltage can be said an energy like quantity

So in simple terms there is no external interaction, a pressure is generated in the cell which is in turn spread throughout the closed loop hence creating a stream of elections drifting from negative to positive terminal which negates the pressure generated by the battery so essentially making ΣV = 0

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.