^Advantages of ac 1. economical than dc. 2. can be easily transformed from low voltage to high voltage or vice versa using transformers. 3. can be transmitted to distant places with comparatively smaller energy losses. 4. can be controlled using choke coils without having appreciable energy losses. 5. can be converted to dc using rectifiers. […]
^Transformer Transformer is an electric device based on of mutual induction used to transfer power from the primary to the secondary by convert low alternating voltage (at high alternating current) into high alternating voltage (at high alternating current) & vice versa without any transfer of charge. Its efficiency is defined as k > 1 for […]
^Choke coil A coil having large inductance & small resistance connecting it in series with a fluorescent tube in order to control current in it without appreciable power loss. Application of chock coil A resistor due to larger power dissipation is not used. For a normal inductor consumes power smaller than consumed by a resistor […]
^Motor starter It is a variable resistor (maximum when the motor is just switched on & its value decreases gradually as the motor picks up the speed) used in the series of the armature to supply the constant current to the motor & thus to protect the motor from burning.
^dc motor Slip ring arrangement used in ac generator is replaced by split ring arrangement in dc motor. Current flowing in the motor is given by . It is maximum when the motor is just switched on as then induced emf is zero. This strong current may even burn the coil. As the motor picks […]
^LC R parallel circuit or rejecter circuit Reciprocal of impedance Z is called admittance Y. Current delivered by the supply is I = I1 + I2 If the source oscillates at angular frequency then imaginary part of Y becomes zero & Y is minimum. This stage is called resonance. Following points are of interest at […]
^LCR series or acceptor circuit If the generator oscillates at a frequency equal to natural frequency of LC oscillator then current in the circuit becomes maximum & the stage is called resonance. Following points are of interest at resonance. 1. XL= XC, Z = min. = R 2. 3. Φ = 0 4. Quality factor […]
^Impedance triangle Impedance triangle is also called ac triangle. It is obtained by the phase relationship between I & V for various elements of a given circuit & is useful to find X, R, Z, Φ, PF, Iv, Pav & WLC. Here X = net reactance of the circuit and R = resistance offered […]
^Power factor Power factor is defined as, . Its value lies between 0 & 1. To decrease the power loss in the transmission we have to increase the power factor, we can do this by making Z tend to R, for this we have to include a capacitor in the circuit.
^Wattless current The average power consumed by a pure inductor & a pure capacitor is zero while that by a pure resistor is maximum. The current flowing in a pure inductor & a pure capacitor doesn’t dissipate any power. Such a current is called wattless current or idle current. Its amount is Iv sinΦ.
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