Normally, the tool meant for measuring current is the ammeter, while the tool for measuring voltage is the voltmeter. By computation, we use mathematical equations or formulas by experimentation we use measuring or test tools. We can determine the value of current and voltage in an electronic circuit computationally or experimentally. Voltage is the pressure moving current, and in fact, the Chinese refer to voltage as pressure. This is because “current will only move from a region of higher voltage or electrical potential to a region of lower voltage or electrical potential. The rule is this current can only flow in the direction indicated by the dark blue arrow and not opposite it. This is like waterfall, water can only flow downwards.įigure 6: Current flow with respect to potential differenceįrom the figure above, point X is at 9V potential, point Y 6V potential and point Z 3V potential. Therefore, know from here that current which formed from charges can only move from regions of higher electrical potential or voltage to regions of lower electrical potential or voltage. This means that it moved from a point of higher potential to a point of lower potential. when it met with –q (because unlike charges attract), that force pushing it from +q tends to zero. When +Q was in-between –q and +q, it had greater force influence which made it to move to meet –q. So, if the charges in an electrical system did work by lighting up a bulb and by doing so exerted some electrical energy if that energy is 10J and the number of charges that did the work is 2C, then, the voltage of the system will be: The unit of Voltage is Volt, which is abbreviated as V. Hence, we conclude that the work a unit positive charge did in moving from Point B to Point C under the influence of surrounding charges ( +q and –q) is called “ Voltage” or electrical potential. By doing work, it has used up energy with time. By moving a distance from Point B to Point C, it has done work. When the above situation happens, the unit positive charge just moved from its initial position (point B) to another position (Point C), towards the direction of the negative charge –q. this unit positive charge will tend to move towards the negative charge -q and away from the positive charge +q.įigure 4: Influence of positive and negative charges on a unit positive charge. Now, if you put a unit positive charge +Q in-between the negative charge denoted with –q and the positive charge denoted with +q, from the fact we established earlier, the unit positive charge +Q will be attracted to the –q and repelled by the +q. In the different scenarios, either an attractive force or a repulsive force is experienced by the charges when they come close to each other. But if one is positively charged and the other negatively charged, they different charges will attract each other. Same thing happens if they are both negatively charged.
they would not want to come much closer to each other. If we have two charges that are both positively charged, the repel each other, i.e. These charges we talked about while explaining current do influence each other when they come close. A charge that does not move can’t be called current. It’s only when a charge moves with time that we can refer to it as current. It should be noted also that current is charge in motion. Electrons are negatively charged and they are charge-carriers in batteries. But when J.J Thompson discovered that it was electrons that do the work in electronic circuits and they are not positively charged, the science community still continued with Benjamin Franklin’s convention, so, we call this virtual current “conventional current”.īut, bear in mind that electrons flow from the negative end to the positive end of the battery. Years back, before the electron was discovered Benjamin Franklin termed any mysterious thing that moves and does work as being positively charged. The reason where we see current as being positive was as a result of past events. But we know that current is created by charges in motion, and charges are carried by electrons which are negatively charged. The direction of current flow is indicated with purple arrows. Figure 3: Current shown as moving from positive end to negative end of the battery.įrom the diagram above, it looks like current is carried by positive charges moving from the positive end of the battery (shown in red color) to the negative end (shown in black color).