Click to Chat
1800-2000-838
+91-120-4616500
CART 0
Use Coupon: CART20 and get 20% off on all online Study Material
Welcome User
OR
LOGIN
Complete Your Registration (Step 2 of 2 )
CURRENT ELECTRICITY Electric current in simple words refers to the rate at which the electric charge flows in an electric field or an electric circuit. Basic concept of current: Electric current can also be defined as the rate of flow of charge through a particular area of cross section of a conductor. The current always flows in a direction which is from a region of higher potential to a region of lower potential. The direction of flow of electrons is opposite to direction of current because they carry negative charge and will move from a region of higher potential. Electric current is a scalar quantity. If we consider the case of water pipes, the water current flowing through the pipe can be assumed to be the electric current. The unit of measurement of electric current is ampere (amp). If we consider the case of electric charges, then the rate at which electric charges pass through a conductor is also defined to be electric current. These charged particles may have any charge either positive or negative. Generally, some kind of force or a push is required by a charge to flow and this force is provided by either voltage or potential difference. The word ‘current’ is indeed an abbreviation for electric current. When we discuss this topic, the context of the situation is such that it automatically implies the adjective ‘electrical’. Current in gases and liquids includes flow of positive ions in one direction and of negative ions in the direction opposite to the first direction. If there exists a current of negative charge which is moving in opposite direction, then even that is included in the total current as it is assumed to be equal to positive charge of the same magnitude moving in the usual direction. Electric current also leads to the formation of magnetic fields similar to the case of electromagnetics. Any kind of heat loss or loss of energy that occurs in a conductor by electric current is proportional to the square of the current. CURRENT DENSITY Current density, as it follows from the word itself refers to the density of the current. Mathematically, current density is the ratio of the electric current that flows in a conductor at a particular point to the cross-sectional area of the conductor. Hence, it denotes the amount of current flowing across a particular area. It is denoted by the symbol ‘J’ and its unit of measurement is amperes per square metre. The mathematical formula for the calculation of current density is given by J = I/A, where ‘I’ is the current in amperes that flows through the conductor. ‘A’ is the cross sectional area in m^{2}. Current density is a vector quantity and has the same direction as that of current. If we consider ‘I’ to denote the total electric current then the relationship between ‘I’ to the current density can be represented as I = ∫ J. dS, where the integral runs over the area where current is flowing This shows that the total current (I) equals the summation of current density over the area where charge is flowing. Illustration: A copper wire of area 5 mm^{2} has a current of 5 mA of current flowing through it. Calculate the current density? Solution: Given: Total Current I = 5 mA, Total Area A = 5 mm^{2} The Current density is given by J = IA = 5×10−3A5×10−3m = 1 A/m^{2}. Drift Velocity: It is a known fact that charged particles don’t travel in straight lines in a conductor due to the obvious reason that they often collide with other particles present in the material. Therefore, the average speed at which the particle travels along the conductor is called the drift velocity. Inn other terms, the drift velocity may be defined as the average or the mean velocity attained by a particle as a result of electric field. It can also be called as the axial drift velocity since the particles are assumed to be moving in the plane. Drift velocity formula: The mathematical formula for calculation of drift velocity in a material exhibiting constant cross-sectional area is given by: v = I/ nAq, where v is the drift velocity of electrons I is the current flowing through the conductor n is the density of the charge-carrier q is the charge on carrier A is the area of the cross-section View the following video for more on the topic The concepts of current and current density are very important for IIT JEE. askIITians offers comprehensive study material covering all the areas like formulation of drift velocity, current through a metallic conductor, constant potential difference, variation of resistivity with temperature etc. the JEE aspirants must master these topics in order to remain competitive in the JEE. Related resources:
Electric current in simple words refers to the rate at which the electric charge flows in an electric field or an electric circuit.
Electric current can also be defined as the rate of flow of charge through a particular area of cross section of a conductor. The current always flows in a direction which is from a region of higher potential to a region of lower potential. The direction of flow of electrons is opposite to direction of current because they carry negative charge and will move from a region of higher potential. Electric current is a scalar quantity. If we consider the case of water pipes, the water current flowing through the pipe can be assumed to be the electric current.
The unit of measurement of electric current is ampere (amp). If we consider the case of electric charges, then the rate at which electric charges pass through a conductor is also defined to be electric current. These charged particles may have any charge either positive or negative. Generally, some kind of force or a push is required by a charge to flow and this force is provided by either voltage or potential difference. The word ‘current’ is indeed an abbreviation for electric current. When we discuss this topic, the context of the situation is such that it automatically implies the adjective ‘electrical’.
Current in gases and liquids includes flow of positive ions in one direction and of negative ions in the direction opposite to the first direction. If there exists a current of negative charge which is moving in opposite direction, then even that is included in the total current as it is assumed to be equal to positive charge of the same magnitude moving in the usual direction.
Electric current also leads to the formation of magnetic fields similar to the case of electromagnetics. Any kind of heat loss or loss of energy that occurs in a conductor by electric current is proportional to the square of the current. CURRENT DENSITY
Current density, as it follows from the word itself refers to the density of the current. Mathematically, current density is the ratio of the electric current that flows in a conductor at a particular point to the cross-sectional area of the conductor. Hence, it denotes the amount of current flowing across a particular area. It is denoted by the symbol ‘J’ and its unit of measurement is amperes per square metre.
The mathematical formula for the calculation of current density is given by
J = I/A, where
‘I’ is the current in amperes that flows through the conductor.
‘A’ is the cross sectional area in m^{2}.
Current density is a vector quantity and has the same direction as that of current. If we consider ‘I’ to denote the total electric current then the relationship between ‘I’ to the current density can be represented as
I = ∫ J. dS, where the integral runs over the area where current is flowing
This shows that the total current (I) equals the summation of current density over the area where charge is flowing.
Illustration: A copper wire of area 5 mm^{2} has a current of 5 mA of current flowing through it. Calculate the current density? Solution: Given: Total Current I = 5 mA, Total Area A = 5 mm^{2} The Current density is given by J = IA = 5×10−3A5×10−3m = 1 A/m^{2}.
Drift Velocity: It is a known fact that charged particles don’t travel in straight lines in a conductor due to the obvious reason that they often collide with other particles present in the material. Therefore, the average speed at which the particle travels along the conductor is called the drift velocity. Inn other terms, the drift velocity may be defined as the average or the mean velocity attained by a particle as a result of electric field. It can also be called as the axial drift velocity since the particles are assumed to be moving in the plane.
Drift velocity formula: The mathematical formula for calculation of drift velocity in a material exhibiting constant cross-sectional area is given by:
v = I/ nAq, where
v is the drift velocity of electrons
I is the current flowing through the conductor
n is the density of the charge-carrier
q is the charge on carrier
A is the area of the cross-section
View the following video for more on the topic
The concepts of current and current density are very important for IIT JEE. askIITians offers comprehensive study material covering all the areas like formulation of drift velocity, current through a metallic conductor, constant potential difference, variation of resistivity with temperature etc. the JEE aspirants must master these topics in order to remain competitive in the JEE.
Related resources:
Click here for the Complete Syllabus of IIT JEE Physics.
Look into the Sample Papers with Solutions to get a hint of the kinds of questions asked in the exam.
Click to know the most Useful Books of Physics
To read more, Buy study materials of Current Electricity comprising study notes, revision notes, video lectures, previous year solved questions etc. Also browse for more study materials on Physics here.
Signing up with Facebook allows you to connect with friends and classmates already using askIItians. It’s an easier way as well. “Relax, we won’t flood your facebook news feed!”
Post Question
Dear , Preparing for entrance exams? Register yourself for the free demo class from askiitians.
Resistance and Resistivity Resistance If...
Basic Concepts In electrostatics we have seen that...
Mechanism of current flow in a metallic conductor...
Electric Current and Current Density Electric...
Specific resistance of the material of a wire...
Maximum Power Transfer Theorem Alternating current...
Grouping of Identical Cells Series grouping E.m.f....
Variation of resistivity with temperature We have...
Measurement of an unknown resistance using a Post...
Emf and Grouping of cells Electromagnetic Force...
Drift Velocity The average velocity attained by...
Errors The major systematic errors in this...
Wheatstone’s bridge The Wheatstone bridge...
Solved Examples of Comlicated Circuits...
Effective grouping of cells The flow of current...
Thermal and Chemical Effect of current The flow of...
Drift Velocity and Ohm’s Law Conductors and...
Constant potential difference Potential difference...
Complicated Circuits As the name suggests,...