Basics of the voltage and current laws explained with images

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Basics of Voltage and Current Laws:

In the image below you can see a very simple circuit consisting of a Bulb, Switch, and a battery. The purpose of adding the switch is to control the Bulb. So, when the switch is open there is no flow of the charges i.e. current, and thus the bulb will remain OFF. The Red color balls represents the flow of charges and furthermore you can see the voltage and the force. The brownish type trace is the wire. The switch is connected in series with the Bulb. Ground from the battery is connected with the ground of the DC Bulb, while the voltage is connected with the +ve of the DC bulb through a switch. So, by turning ON and turning OFF the switch, the current flow can be controlled.

For now let’s imagine that the switch is Open. There is no flow of current or charges and as a result, you can see the Bulb is in the OFF state, as shown in the image below.

While the battery is connected, now to turn ON this bulb we will need to turn on the switch to make a close path, so that the charges can flow due to the closed loop.

The same principle applies to multiple or several light Bulbs. We can use one switch to control all the Bulbs or each Bulb can have its own individual switch to control. These switches will control the flow of charges that we often called as the current.

The charged particles flow through the light bulb because the battery causes them to have a higher potential energy on one side of the light bulb than the other you. This P.E or Potential energy is referred to as the voltage.

If same voltage is available on both the ends or sides of the light Bulb then now current will flow, this is same as applying equal force on a box from opposite direction, of course the box will remain stationary. Let’s say initially the voltage is at 0 level. When you gradually start increasing the voltage the bulb will start to glow, initially the light intensity will be low due to the small voltage. But as you continue to increase the voltage, the light brightness will start to increase. You can continue to increase the voltage to its rated voltage. If you further increase the voltage beyond the rated voltage the bulb will be damaged.

For the current to flow, the loop should be closed. If the voltage is connected but the ground is not connected then the light wont ON. Likewise, if the ground is connected but the voltage is disconnected still the light bulb won’t turn ON. As I said earlier, for the same voltage there will be no flow of the current or charges.

As you know we have different batteries, available in different sizes and capacities. Some batteries are rated at 1.5V, 3 volts, some at 6volts, and some at 12volts, etc, so no matter which type of the battery you are using the difference in voltage across its terminals is always at a specific value. So all the electrical devices connected through metal conductors will receive the same voltage, let me make it more simpler, if multiple bulbs are connected in parallel with the battery, the voltage across all the bulb will be the same. As the voltage determines how much current will flow through the bulb so the current through all the bulbs will be the same as they are connected in parallel. As the battery starts to discharge, the voltage will start to reduce and so the current. But still the voltage and current across all the bulbs will remain the same. The voltage will always remain the same.

For the bulbs connected in parallel the total current is equal to the current drawn by all the bulbs.

Let’s consider another situation where multiple light bulbs are connected in series. You know, in parallel circuits the voltage is same but the current is different, while in the series circuit the current is same and the voltage is different. So, for a series circuit the current entering into the circuit should be equal to the exiting current. So when the light bulbs are connected in series, due to the voltage drop across all the light bulbs less current will flow due to which the bulbs brightness will reduce.

Let me explain this in more simple way.

Let’s say we have two 12V bulbs connected in parallel with a 12v battery. As I said earlier in parallel circuit the voltage remains the same, so both the bulbs will get 12Volts and the bulbs will glow brighter.
Let’s assume the same 12V bulbs are now connected in series with the same 12V battery. As you know in series the voltage is divided. So this time each bulb will receive only 6volts, due to which the bulbs will glow with less brightness. I am sure now you got it ;).

As per the Kirchhoff’s current law, the sum of currents flowing towards the junction is equal to the sum of currents flowing away from the junction. Read my article on “Kirchhoff’s Laws, Kirchhoff’s Voltage Law & Kirchhoff’s Current Law”. In this article I have explained everything in very detail along with some examples.

This is accompanied by another law called kirchoff’s voltage law which states that “the algebraic sum of all the voltages taken in a specified direction taken around the closed loop is zero”.