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Electric Current

  • Last Updated : 30 Apr, 2021

There existed a time when no electronic devices were available, devices like laptop, cellphones, there even was a time when humans did not have a fan to cover the heat, light in the house to see in the dark, but in today’s time, People have all these in their hands’ reach, all this was possible because of one invention — “Electricity”. Electricity is the flow of electric charges when a potential difference is available at the ends of the wire. It will not be incorrect to say that Humans mostly rely on Electricity not only for easy living, but it has become a way of life. From Rockets to Trains to Factories to our home appliances, everything works on electricity.

What is Electric Current?

The flow of electric charges is known as electric current. Earlier when the electrons were not discovered, it was said that electric current is the flow of positive charges, The flow of current and the current itself is generated due to the movement of negative charges (electrons), electrons flow from negative terminal to positive terminal (lower to higher potential) which is known as the Electron flow while current flows from positive terminal to negative terminal (Higher to Lower Potential) which is also known as the Conventional current flow.

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The best way to imagine current flowing in a circuit is by imagining flow of liquid inside a pipe from a higher point to lower, the liquid represents current, the difference in the heights of the extreme end of the pipe represents the difference in potential causing the current to flow if the pipe is twisted at some point the flow of the liquid will slow down, that represents the resistance offered by the conductor that reduces the current.

Formula for Electric current 

The electric current can be represented as the rate of flow of electric charge (q), Electric charge comes under the basic units like mass, length, and so on. The unit of Electric charge is Coulomb and therefore, the unit of Electric current becomes Coulomb/sec.

I = q/t

Unit of Electric Current

The Unit of electric Current is Amperes (A) or Coulomb/second.

Electromotive Force 

Normally, in a conductor, Electrons are present, and they are not stationary, they keep on moving in random directions, and due to their randomness, the overall displacement of all electrons becomes zero and hence, no current is produced. In order to produce current, some external force is required to align electrons in one direction and make them move in that one direction, the external force is known as Electromotive Force and is also famous as EMF. It is nothing but the voltage applied to produce current.

Properties of Electric Current

  • Current is due to the Flow of electrons in the circuit.
  • Electric current can be categorized as AC and DC in nature, where DC is the direct current that flows in only one direction, DC is used in low-voltage applications, aircraft applications, etc. AC is known as alternating current, and it flows in both directions alternatively, AC is the current that comes in our houses and the appliances work on AC.
  • Electric current in a circuit can be controlled by introducing resistance to the circuit.
  • The unit of Electric current is Amperes (A). 1 Ampere can be defined as the flow of 1 coulomb of charge in 1 second.
  • Electric current flows from Higher potential to Lower Potential in a circuit (from positive terminal to negative terminal) also known as the conventional current flow direction.

Ohm’s Law

The German physicist Georg Simon Ohm stated that the current flowing in a wire is directly proportional to the voltage drop across it. According to Ohm’s Law, the current flowing through a wire is directly proportional to the voltage applied at the ends of the wire provided that the temperature and conductivity remains the same.



Upon removing the proportionality sign, a proportionality constant is introduced known as Resistance.

V ∝ I

V = RI

V= Voltage at the ends of conductor

R= Resistance offered by the conductor

I= Current through the wire.

Effect of Electric Current

There are different effects that can be noticed due to the flow of electric current in a wire, for example, when current passes through a resistor, the resistor has a property of resisting which does not let the whole current pass but since energy can neither be created nor destroyed, it is converted in heat energy and is released in the form of heat, this effect is called as the heating effect of current. Similarly, we have magnetic and chemical effects of electric current.

Chemical effect of Electric Current

When Electric current is passed through a which is conducting in nature, the solution breaks in its respective ions, and effects are seen visibly. The major effects that are prominent,

  • The color of the solution may change.
  • The deposition of metal at the electrodes may be seen.
  • There can be the formation of gas bubbles at the electrodes.

Magnetic effect of Electric current



Electric current is nothing but the motion of electrons, and it is known, when charges are stationary, they create Electric Field but when charges are in motion, they create a Magnetic field. When current is passed through a wire and a metallic sheet is placed there with a needle, the needle will be deflected due to the presence of a magnetic field which is produced by the electric current. One of the biggest applications of the Magnetic effect of electric current is Electromagnets, they are formed with the help of passing current.

Heating effect of electric Current

When current flows in a conductor, heat energy is produced and released from the conductor and the amount of effect depends upon the resistance offered by the conductor. If the conductor has to offer high resistance, it simply means that it shall not allow most of the current to flow but due to the conservation of energy (energy can neither be created nor destroyed), current that could not pass is converted into heat and the phenomenon is known as Heating effect of current. The formula for heat energy is given by,

H = I2RT

Where, H= Heat energy released

I= current flowing in the conductor

R= Resistance offered by the conductor

T= Time for which the current was flowing in the conductor.

Applications of heating effect of current involve Electric Irons, Electric Heaters, filament lamps, Electric kettles, etc.

Sample Problems

Question 1: In a conductor, 10 Coulombs of charge flows for 5 seconds, determine the current produced?



Solution:

The current in a circuit is given by,

I = q/t

I = 10/5 Amperes

I = 2 Amperes

Therefore, 2 amperes of current flows in the circuit.

Question 2: Answer the given questions,

1. Which material is a better conductor of electricity — Iron or Silicon?

2. What is the best conductor of electricity? 

Answer: 

1. Iron is a better conductor of electricity while silicon is a semiconductor.

2. Silver is known to be the best conductor of electricity.

Question 3: In the circuit given below, Find the current flowing through the circuit.

Solution:

In the figure provided, it is clear that there are two resistances, and they are in series. When two or more than two resistances are attached in series in a circuit, the overall resistance becomes equal to the sum of individual resistances present in the circuit.

R = R1+ R2

R = 2+ 2

R = 4 ohms

From Ohms Law, 

V = IR

I = V/R

I= 20/4

I= 5 Amperes 

Question 4: Why Silver is not used more often as a conductor in daily usage?

Answer:

Silver is known to be the best conductor of electricity but is still not preferred to be used in daily usage as a conductor because of its unavailability and the fact that silver is very expensive. Instead, conductors like copper which are easily available are used.

Question 5: What is the Heat energy produced when 2 amperes of current is flowing in a circuit for 5 seconds having an overall resistance in the circuit of 4 ohms?

Solution:

The Heat energy produced is given by,

H= I2RT

H= (2)2×4 × 5

H= 16 × 5

H= 80 Joules

Therefore, 80 Joules is produced in the circuit.




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