The Philosophical magazine; a journal of theoretical, experimental and applied physics . )Ioyed, enables the power given to theprimary coil to be measured from one reading without theknowledge of either the resistance or the coefficient of self-induction of the primary. Let the two (»oiIs of the electrodynamometer be A and B,and let their resistances and coefficients of self-induction be ri/2 and l^J-j respectivelv; moreover, let — = —, that is to say, let the time-constants of the two coils be the same ; this canbe easily eflfected by putting an inductionless resistance inseries with one or o
The Philosophical magazine; a journal of theoretical, experimental and applied physics . )Ioyed, enables the power given to theprimary coil to be measured from one reading without theknowledge of either the resistance or the coefficient of self-induction of the primary. Let the two (»oiIs of the electrodynamometer be A and B,and let their resistances and coefficients of self-induction be ri/2 and l^J-j respectivelv; moreover, let — = —, that is to say, let the time-constants of the two coils be the same ; this canbe easily eflfected by putting an inductionless resistance inseries with one or other of the coils. Connect as in Let the primary coil be put in series with an inductionlessresistance R. Let the potential-difference between Vj and V2= Eisinaf ; then i, the current through the primary coil and CI through if ^^^^ {p-^~^)^ where E2 is the maximum poten-tial-difference between V2 and V3. Let i^i and y^r^ be the angles of lag of the coils A and Brespectively, and let ?, and Io be the currents through them atsome instant t. Then, if h be the reading of the torsion-head, S = mv I ii4 dt, ^ T g^. 1 ^^ ^ ~^^^ ^^ {at-yfr -y\r^)dt, _k E1E2Phil. May. IS. 5. Vol. 25. No. 157. Jun^ 1888. cos (-v|/-i — -v/to — y^) ; 2 K 486 Power supplied to the Primary Coil of a Transformer. where Si = v/ri- + a-/,2 and Sg = \/r/+ a^/g. Now Hence or Therefore tan> — and tan-»/r.,= ^=-rj ^ - 7-2 tan 1/^1= tan -ylr^, since - = -? Now mean power given to the primary coil, or EiEg , o S1S2 For permanent enrrents, Also K |a, where ^ is the constant for watts. HenceTherefore ;l = Pr, 3^ . S . ^1^2. Si S2 may be
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