Induced EMFWhen a magnetic flux linking a conductor or coil changes, an electromotive force (EMF) is induced in the conductor or coil, is known as induced EMF. Depending upon the way of bringing the change in magnetic flux, the induced EMF is of two types −Statically Induced EMFDynamically Induced EMFStatically Induced EMFWhen the conductor is stationary and the magnetic field is changing, the induced EMF in such a way is known as statically induced EMF (as in a transformer). It is so called because the EMF is induced in a conductor which is stationary. The statically induced EMF can also ... Read More

Hysteresis LossWhen a magnetic material is subjected to cycle of magnetisation (i.e. it is magnetised first in one direction and then in the other), a power loss occurs due to molecular friction in the material i.e. the magnetic domains of the material resist being turned first in one direction and then in the other. Therefore, energy is required in the material to overcome this opposition. This loss being in the form of heat and is termed as hysteresis loss. The effect of hysteresis loss is the rise of temperature of the machine.The formula for the calculation of hysteresis loss is ... Read More

When electric current is passed through a conductor, heat is generated in the conductor. This effect of electric current is known as heating effect of electric current.In practice, when electric current is passed through the element of an electric heater, the element of the heater becomes red hot, because the electrical energy is converted into the heat energy. This is called heating effect of electric current and is used in manufacturing of many heating appliances like electric iron, electric kettle etc.Cause of Heating Effect of Electric CurrentWhen a potential difference is applied across the ends of a conductor, the free ... Read More

When a current carrying conductor is placed at right angles to a magnetic field, it is found that a force acts on the conductor in a direction perpendicular to the direction of both the magnetic field and the current.ExplanationConsider a straight conductor carrying a current of I amperes. If the magnetic flux density is B, the effective length of the conductor is l and θ is the angle which the conductor makes with the direction of the magnetic field.It has been found by experiments that the magnitude of the force (F) acting on the conductor is directly proportional to −Magnetic ... Read More

An English electrical engineer and physicist Sir John Ambrose Fleming established two rules, known as Fleming's Left-Hand Rule and Fleming's Right-Hand Rule which are widely used in electrical machines.When a current carrying conductor is placed in a magnetic field, a mechanical force acts on the conductor. The direction this force is determined by Fleming's Left-Hand Rule. The left-hand rule is mainly applicable in electric motors.Also, when a conductor is moved in a magnetic field, an emf is induced in the conductor due to which an electric current flows in the conductor. The direction this induced current is determined by Fleming's ... Read More

Faraday’s Laws of Electromagnetic InductionMichael Faraday (an English scientist) performed a series of experiments to demonstrate the phenomenon of electromagnetic induction and he summed up his conclusions into two laws, known as Faraday's laws of electromagnetic induction.First Law of Electromagnetic InductionThe first law states that "when a magnetic flux linking a conductor or coil changes, an EMF is induced in the conductor or coil". Therefore, the first law tells about the condition under which the emf is induced in a conductor or coil.Second Law of Electromagnetic InductionThe second law states that "The magnitude of the induced emf in the conductor ... Read More

Consider a coil of N turns wound around a magnetic core and is connected to voltage source (see the figure).By applying KVL, we get, $$\mathrm{V = e+iR\:\:\:\:\:\:...(1)}$$Where, e is the induced EMF in the coil, R is the resistance of the coil circuit.The instantaneous power input is given by, $$\mathrm{p = Vi = e+i^{2}R\:\:\:\:\:\:...(2)}$$Hence, the energy input to the system is, $$\mathrm{W_{i} =\int_{0}^{T}=p\:dt=\int_{0}^{T}ei\:dt+\int_{0}^{T}i^{2}Rdt\:\:\:\:\:\:...(3)}$$The eq. (3) shows that the total input energy consists of two parts. The first part is energy stored in magnetic field and the second part is the energy dissipated in the circuit resistance in the form of ... Read More

A doubly-excited system is the type of magnetic system in which two independent coils are used to produce magnetic field. Examples of doubly-excited systems are synchronous machine, separately excited DC machines, loudspeakers, tachometers etc.Consider a doubly-excited system as shown in the figure, it consists of a stator wound with a coil having a resistance of R1 and a rotor wound with a coil of resistance R2. Both the coils are excited by independent voltage sources.Following assumptions are made to analyse a doubly excited system −For any rotor position the relationship between flux-linkage (ψ) and current is linear.Hysteresis and eddy current ... Read More

An AC motor is an electromechanical device which converts electrical energy input into mechanical energy. The AC motors are mainly classified into two types viz.Asynchronous or Induction MotorSynchronous MotorAsynchronous or Induction MotorAs the name implies, the asynchronous motors are the ones whose speed is not equal to synchronous speed, i.e. these motors run at a speed slightly less than the synchronous speed. The induction motors are the types of asynchronous motors.The induction motor consists of a stator and a rotor. The stator carries a 3-phase winding while the rotor carries a short circuited winding. When the stator winding is energised ... Read More

Electric Power: DefinitionThe rate at which work is done in an electric circuit is known as electric power. In other words, the energy used per unit time in an electric circuit is called as electric power.Electric Power: FormulaAs, the electric power is the rate of doing work in an electric circuit, thus, $$\mathrm{Electric\:power, P=\frac{Work\:done\:in\:elecric\:circuit(W)}{Time(t)}}$$Consider an electric circuit shown below. An electric current flows in the circuit, when a voltage is applied to it. So, work is being done in moving the charge (electrons) in the circuit. This work done in moving the charge per unit time is known as electric ... Read More