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MHT-CET : Physics Entrance Exam

MHT - CET : Physics - Electomagnetic Induction Glossary

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         Magnetic Flux: The magnetic flux f through an area is defined as f = . = BA cos q where q is the angle made by with .

A coil of area in a
uniform magnetic field

          

         Faraday's Law: The magnitude of induced e.m.f. in a circuit is directly proportional to the rate of change of flux through the circuit.

e  

df

dt

          

         Lenz's Law: The direction of induced e.m.f. is such that it opposes the cause that produces it.

\ e = - 

df

dt

          

         Self Induction: The phenomenon of induction of an e.m.f. in a coil due to change in the current flowing through the same coil.

         Mutual Induction: The phenomenon of induction of an e.m.f. in a coil due to change in the current flowing in a neighbouring coil.

         Induction Coil: It was deviced by Ruhmkorff in 1851. This is a device by which a direct current at low voltage is converted into intermittent direct current at high voltage.

         Earth Coil: It is a device which is used to measure the vertical and horizontal component of the earth's magnetic field and the angle of dip.

         Phase Difference: The phase difference between two alternating quantities indicates the lead or lag of one quantity with respect to the other.

         R.M.S. Value of an A.C.: The root mean square (r.m.s.) value of an alternating current is the value of the direct current which produces the same amount of heat in the same time in the same conductor.

         Capacitive Reactance:

 

The quantity XC

1

 is called the capacitive reactance of a capacitor and is a measure of

2p fC

         the opposition offered by the capacitor to the flow of the alternating current.

         Inductive Reactance: The quantity XL = 2pfL is called the inductive reactance and is a measure of the opposition offered by an inductor to the flow of the alternating current.

         Impedance of an L-C-R Series Circuit: The total opposition offered by a circuit containing an inductance L, a capacitor C, and a resistance R and an alternating source is given by Z = . The quantity Z is known as the impedance of the circuit.

         Resonant Circuits:

(a) Series Resonance: An L-C-R series resonant circuit is shown below.

        
In this circuit, the reactive component of the opposition offered to the ac current becomes zero at a certain frequency called the resonant frequency. Therefore, the current in the circuit is maximum at this frequency.

f0 =  

1

2p

        

(b) Parallel Resonance:

        
When frequency
f0 of a.c. source is such that = w0C, the line current in the circuit becomes minimum (zero). An oscillatory current flows between L and C. This phenomenon is known as parallel resonance. Resonance frequency is given by

f0 =  

1

2p

                    

 

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