how does current and voltage work
We will learn some basic concepts in today’s blog: voltage, Current, and resistance. These are the basic building blocks. It is challenging to understand voltage and current because we cannot “see” them with naked eyes. Still, I cannot say we cannot feel their presence because you’re obviously going to burn to a toast once you touch a circuit. Not everyone can wield electricity like Thor and Zeus.
So apart from that, let’s move towards our first topic.
Voltage
The voltage or potential difference is the energy required to move a unit charge from one point to another
As the name suggests, it is the difference between two potential.
From the previous blog, we learned that how negatively charged electron moves freely. Still, some kind of force has to pull the electrons from one place to another. This attractive force between positive and negative charges is called electromotive force.
Consider a battery connected to a bulb through a conductor. We cannot expect the electricity to flow. We need something to trigger the electricity, and that thing is a potential difference.
The positive terminal is considered at a higher potential than the negative one. This causes the flow of charge, which ultimately leads electricity to flow.
Volt is the unit of voltage. It is named in honor of Alessandro Volta(1745-1827)an Italian physicist who invented the battery, which provides the continued flow of electricity.
Current
Current is a flow of charge (generally electrons)
When we provide potential difference (voltage ) to another end, the negatively charged electrons from lower potential start repelling each other due to the supply polarity and get attracted toward the positive terminal ( higher potential). This flow of charges is none other than the Current.
The conventional flow of Current is from higher potential to lower (positive to negative), but the electron flow is the opposite.
Types of Current
- Direct Current (DC) –It is an current that is unidirectional. So the flow of charge is always in the same direction
- Alternating Current (AC) – It is an electric current whose direction reverses periodically.
The current unit is “Ampere” after the scientist Andre Marie Ampere (1775-1836), French scientist, founder of the science of electrodynamics which is nowadays known as electromagnetism.
Current or Voltage : what came first?
Just like Which came first in between Chicken and Egg, this is not that confusing.
If there is a voltage applied across a conductor, electric current will flow. If you have an electric current flowing through a conductor, there will be the voltage across the conductor. Don’t worry about which came first.
Resistor
The resistor is the passive(which does not generate power) electrical component whose primary function is to limit the flow of electric Current.
Resistance is the property of the resistor to oppose Current.
The formula for resistance is,
R= ρl/A
Where ρ= resistivity (resisting power of material)
L= length of conductor
A= Area of cross-section
From the above formula, we can say that if resistance is directly proportional to the length and inversely proportional to area.
Which is very helpful while preciously controlling the resistance of the material.
German physicist George Simon ohm. Who also gave us the ohms law, which provides the relation between current, voltage, and resistance.
The unit is symbolical as an uppercase Greek letter omega.
Ohms law
We all know that ohms law is invented by George ohms. Before him, henry Cavendish experimented with the Leyden jar (as we explained it in our previous blog) and glass tubes of various lengths and diameters filled with the salt solution. He measured the Current after getting a strong shock after completing the circuit with his body. But he never published his work.
The ohms law states that the ratio of potential difference (v) between any two points to the Current (I) flowing through them is constant.
Provided the temperature of the conductor does not change.
In other words,
V/I = constant, or V/I = R
Where R is the resistance.
In simple words, if we kept the R constant, the Current is directly proportional to the potential difference between two points.
i.e., an Increase in Potential difference increase the Current.
Capacitor
A capacitor (condenser) is a device that stores electric charge.
It is a passive element with two (positive and negative) terminals.
The effect of capacitor known as capacitance.
The capacitor consists of two parallel plates separated by a dielectric material, which can charge and release its energy much faster. Because of this feature, it is commonly used for energy storage in devices.
Charging and discharging of capacitor
Before the charging process, the capacitor is at a neutral state (equal positive and negative charge).
When the supply is connected across capacitor terminals, electrons from the capacitor get attracted towards the positive terminal and repelled from the negative terminal. Over time, the top plate becomes positively charged (all positive charge settles on upper plate). The lower plate becomes negatively charged(all negative charge settles on the lower plate).
The building of charges across two plates will continue till the potential difference between two plates is equal to supply voltage. Once the capacitor charged up to supply voltage, if we connect a bulb(as a load)through a conductive path, the negatively charged electrons start flowing toward the upper plate due to force of attraction, so because of the flow of Current, you will see a bulb glow in this way Current will flow through the conductive path and will cause the capacitor to discharge.
The capacitance (c) = Q/V
From this formula, you can observe that you need to apply more voltage across the capacitor if you want to store more charge.
We can conclude that by changing the applied voltage, we can change the amount of charge stored across the capacitor.
The capacitor unit is the “farad,” but it is a substantial quantity to measure the charge, so we use smaller units such as μF (micro-farad), pF(Pico- farad)
Inductor
The inductor is a coil wrapped around a magnetic material.
It is also called a coil or choke. It is a passive element and stores energy in the form of a magnetic field when current flows through it.
Typically it is an insulated wire wound into a coil.
Current flowing through the inductor creates a magnetic field, and magnetic fields are uniform. As a result, an inductor is a device that tries to prevent the changing Current from flowing through it.
If the amount of current flowing through the inductor is constant, it will not generate any forces on the charged particles flowing through it. In this case, the inductor behaves just like an ordinary wire.
On the other hand, if we try to interrupt the current flowing through the inductor, the inductor will generate a voltage, that tries to keep the Current through it.
Suppose an inductor is connected to itself, and there is no resistance in the circuit. The current will theoretically continue circulating forever.
However, unless we are using superconductors, all wires have some resistance, and the current will eventually decay to zero.
Once the current is at zero, the inductor will want to keep the current at zero. An inductor tries to prevent the current flowing through it from changing.
The inductor unit is henry (H). It is named after joseph henry (1797-1878), an American scientist.
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