Category : 10th Class
Electricity & Magnetic Effects of Electric Current
Electricity is the identity of modernity. It has really redefined the way of our life. Thus it has an important place in modern society. It is used almost at every place to facilitate modern activities.
Electric Current
Electric current is the rate at which charge passes by a point in the circuit. The magnitude of electric current in a conductor is the amount of electric charge passing through a point of the conductor in one second.
The SI unit of current is ampere.
A current of 1 ampere means that there is 1 coulomb of charge passing through a cross section of a wire in 1 second.
Electric Circuit
Electric circuit is an incessant conducting path that consists of wires, electric bulb and switch between the two terminals of a cell or a battery along which an electric current
Electric Potential (V)
Electric potential at a point is defined as the work done in moving a unit positive charge from infinity to that point. The S.I unit of electric potential is volt.
Electric circuit
Potential Difference
Potential difference is defined as the amount of work done in moving a unit charge from one point to the other point.
\[V\,=\frac{W}{Q}\]
Where, V is potential difference
W is work done
Q is charge moved
Heating Effect of Electric Current
Through a high resistance wire when an electric current is passed, it becomes very hot and produces heat. This phenomenon is known as Heating Effect of current.
\[H={{I}^{2}}RT\]
Where H = heat produced
I = current
R = resistance of wire
T = time, for which current is passed
This is known as Joule's law of heating.
Ohm's Law
Ohm's law represents the relationship between current and potential difference. According to Ohm's law the current flowing through a conductor between two points is directly proportional to the potential difference and inversely proportional to the resistance between them when the temperature and pressure remains the same.
\[V\,\alpha \,I\]
\[V=IR\]
So, \[I=V/R\]
Where, I is the current v is the potential difference R is the resistance.
Electric Power
Electric power is the electric work done per unit time. The S.I unit of electric power is
\[Power=\frac{Work\,done}{Time\,taken}\]
\[P=\frac{W}{t}\]
By substituting from W = VIt, we obtain the formula for the power dissipated in an electric circuit, as follows:
\[Power\,P=VI\]
This formula gives the power which is degenerated when a current I moves through a conductor when there is a potential difference V. From Ohm's law, we can write:
Power \[P={{I}^{2}}R\] and \[P={{V}^{2}}/R\]
Magnetic Field
Magnetic field is the space/region around a magnet in which magnetic force is exerted. Electric current produces magnetic field. The SI unit for magnetic field is Tesla. The strength of magnetic field is indicated by the degree of closeness of the field lines. Where the field lines are closest together, the magnetic field is the strongest.
Maxwell RightHand Thumb Rule
Right Hand Thumb Rule is a convenient way of finding the direction of magnetic field associated with a currentcarrying conductor. Suppose that you are holding a current carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field. This is known as the RightHand Thumb Rule.
RightHand Thumb Rule
CurrentCarrying Conductors Having Different Shapes Produce Different Patterns of Magnetic Field
Shape of Current Carrying Conductor 
Characteristics of Magnetic Field 

1.Striaght conductor 
v The magnetic field lines around a straight conductor are concentric circles. v The magnitude of magnetic field produced is directly proportional to the current passing in the wire and inversely proportional to the distance of that point from the wire. 

2.Circular Loop 
v The magnetic field lines are circular near the current carrying loop. v The magnitude of magnetic field produced is directly proportional to the current passing through the circular loop and inversely proportional to the radius of circular loop. 

3. Solenoid 
v The magnetic field lines leaves the north pole of a magnet and enters to south pole. v The magnetic field lines inside the solenoid are in the form of parallel straight lines. 

Fleming's LeftHand Rule for the Direction of Force
This rule states that when you stretch your thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. Then the thumb will point in the direction of motion or the force acting on the conductor. The forefinger will points in the direction of magnetic field and the middle finger points in the direction of current.
Fleming's LeftHand Rule
Electric Motor
An electric motor is a device that uses electrical energy to produce mechanical energy by the interaction of magnetic fields and currentcarrying conductors.
Electric motors are used to perform many tasks. They are used in industrial fans, blowers and pumps, machine tools and household appliances. They are also used in power tools, computer disk drives and many other applications. Electric motors may be operated by from a battery in a portable device" or motor vehicle. They are also operated from AC from a central electrical distribution grid.
Electric Generator
An electric generator is a device that converts mechanical energy to electrical energy by using electromagnetic induction. The electric generator works on the principle that there is change in magnetic field around a coil, the current is induced in it.
Electric Generator are of Two Types
(1) Alternating current generator
(2) Direct current generator
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