com www.GOALias.blogspot.com

www.GOALias.blogspot.comPhysicsPhysical quantity Symbol Dimensions Unit Remarksrms voltage V [M L 2 T –3 A –1 ] V V =v m2, v mis theamplitude of the ac voltage.rms current I [ A] A I =i m2, i mis the amplitude ofthe ac current.Reactance:Inductive X L[M L 2 T –3 A –2 ] Ω X L= ω LCapacitive X C[M L 2 T –3 A –2 ] Ω X C= 1/ ω CImpedance Z [M L 2 T –3 A –2 ] Ω Depends on elementspresent in the circuit.Resonant ω ror ω 0[T –1 1] Hz ω 0= for afrequencyLCseries RLC circuitQuality factor Q DimensionlessQω L10= = for a seriesR ω0CRRLC circuit.Power factor Dimensionless = cosφ, φ is the phasedifference between voltageapplied and current inthe circuit.POINTS TO PONDER1. When a value is given for ac voltage or current, it is ordinarily the rmsvalue. The voltage across the terminals of an outlet in your room isnormally 240 V. This refers to the rms value of the voltage. The amplitudeof this voltage is264vm= 2V= 2(240) = 340 V2. The power rating of an element used in ac circuits refers to its averagepower rating.3. The power consumed in an circuit is never negative.4. Both alternating current and direct current are measured in amperes.But how is the ampere defined for an alternating current? It cannot bederived from the mutual attraction of two parallel wires carrying accurrents, as the dc ampere is derived. An ac current changes direction