Show WHAT inductance MEANS EXPLAINED its cause and effects are here told in popular language for the novice when a conductor cuts a magnetic field a voltage Is induced in the con ductor the voltage induced depends for its value on the rapidity with which the conductor cuts the magnetic field the value of the induced volt age Is a function of the rate ot of cut ting ong not of the field density etc A conductor carrying a current Is surrounded by a magnetic field if the value of the current be decreased the magnetic field will decrease in decreasing the magnetic field about the conductor will cut the conductor and induce in it a voltage this induced voltage in a conductor caused by a change in the magnetic field which was produced by the conductor Is called the electromotive electro motive force of belt self indue tion the direction of the induced voltage due to self induction Is such as to oppose any change looking at the end of a conductor it if applied current Is in a direction away from the observer a reduction in current will produce an e in f of self induction that will add to this cur rent flow away from the observer or br being the same direction as the applied voltage an increase in the flow of the current will increase the mag betic field and an e in f of self in will be induced that will oppose the flow of current suppose we consider the magnetic field about a conductor carrying an alternating current the current al erna tely flows in one direction and tween two circuits linked by a mag attic field I 1 ut separated electrically i I 1 samples of both types of induct ance are lound found in bali high and low frequencies in a trans mitter the filter react ances are ex amiles ami les if t low frequency self indue duc tion the filament transformer Is an example ot of mutual inductance the primary in ary of the filament transformer sets up a magnetic field tt tl at Is cut by the conductor that forms tl e beconi if f ary of the transformer in ladio radio fre 6 quency circuits a tuning timing coll coil depends for its action upon sett self ia induction the operation of a loose coupler depends upon mutual induction for the trans ter fer of energy from the primary or antenna circuit to the secondary tu tuned ned circuit to which the rectifying atus la Is connected i skin effect Is due to self induction in a conductor carrying direct current resistance drop which can be consid o 0 ered as a back voltage Is constant over the entire cross section of the con ductor the applied voltage then la Is opposed pt any point on the cross section ot of a conductor by the same back I 1 voltage and hence the current flowing 0 distributes itself evenly over the cross t I 1 1 section of the conductor this Is not true in conductors car crying alternating current there are two voltages that of oppose pose the ilo alov v of f alternating current in a conductor first the back voltage due to resist ance and second tl tie e back voltage in deuced by self in luction the magnet ic lc field surrounding the conductor will i be strongest at the center of the con ductor and weaker at the s of the conductor this will baube u the induced back e 0 in t f to be largest at the center and smallest at the surface of the conductor naturally the den sity of the circuit that flows will be inversely proportional to this opposing e rn t f or the least current will flow at the center and the greater current will flow along the surface As the frequency of the current Is 1 increased the skin effect as it Is 1 fc called becomes more and moie pro aa bounced finally at radio frequencies f yea AL A e tin BACK RACK HF cue DUE to INDUCTS fig I 1 then the other direction each time the direction of flow of the current changes the direction of the magnetic field reverses when an alternating current flows in a conductor the current which Is set up by the changing magnetic field Is 1 also alternating suppose that fig 1 represents a graph of the current flow ing in the conductor during the first quarter of the cycle while the cur rent Is increasing from zero at A to a maximum value at B the magnetic field will build up with ane j current the inductive back e m f which depends on the rate of change of flow will mill be a maximum at A where the flux Is changing most rapidly and a minimum at B where change in flow Is zero similarly during the other three quarters of a cycle the ind induced induction will be a e in t f due to maximum at 0 and E and a minimum at D the dotted curve then in fig I 1 represents the e in t f of self indue tion note that there Is a phase dif ference of one quarter of a cycle or 00 90 electrical degrees between the e in t f due to induction and the current pro producing the magnetic field this ac tion of the conductor having a back e in t f induced in it when a varying current flows through the conductor Is called self induction in other words self induction may be defined as the property of an electrical circuit that tends to prevent any change in the value of the circuit flowing through it the e m f of self induction Is always in such a direction as to prevent any change of current in the circuit A length of wire wound in the form of 0 a coll coil called a solenoid has a greater self induction than the same length of straight the self in of a coll coil with no iron near the magnetic field Is a constant and depends on the physical dimensions of the circuit the unit of inductance Is the henry an electrical circuit has an inductance of one henry when a change in the current of one ampere per second will cause a back e in f of one volt it has been explained that an ever changing magnetic field surrounds a circuit carrying an alternating current and that tits changing magnetic field induces in the circuit a back e in t f which opposes any change in the current flowing in the circuit if a second electrical circuit Is brought within the magnetic field of the first circuit the second circuit will have a voltage induced in it the val ue of the voltage induced in the sec see ond electrical circuit will be one volt per lines of flux cut per second the direction of the induced voltage in the second circuit will be electrical degrees 0 it ii or phase with the applied voltage of the first circuit the phenomenon just described Is known as mutual induct ance self induction Is the reaction of a circuit upon itself mutual induct ance Is the reaction that exists be such a quan tit of curlent flow flows near the center of the conductor that the conductive material mat crial there thero Is useless and can be removed I 1 lor or this reason tubing Is 1 often used for con 4 ducting high power at high frequez cles |