Dear ak__tevar
Pageno 80 level 2 problems,
(21)V= 10 sin (wt+30)
I = 10 sin (wt-30)
Instantaneous Power consumed in the circuit P(t) = V(t)I(t)
Utilize expression for sin(A+B)sin(A-B).
Double freq. terms yield zero average, leaving only 25W is the required power consumed in the circuit.
(22)An ideal transformer
(a) Is an abstract concept- since leakage and core losses cannot be zero.
(b) One where the voltage and current relations are derived from Faraday’s law and Ampere’s law respectively –
Current Relations
closed line integral H.dl = N1Io (during no load condition)
Since core flux does not change from no load to full load condition,
closed line integral H.dl = N1I1+N2 I2 (during loaded condition)
Consequently N1I1+N2 I2 = N1Io
N1Io is small, therefore N1I1 -N2 I2
Voltage relations, E = 4.44 f N m comes from Faraday’s law
(c)Is characterized by a single parameter ratio n, the turns ratio which is evident from the equivalent circuit.
Thus a, b, c are true and the correct option is D
(28)Just before the completion of 2 sec, the inductor current is 8A (I = 4t; 0<t<2). Since the circuit does not have any resistor, the entire inductor energy is dissipated at the switching contacts during the with drawl of the 4V pulse.
Hence current at t = 3s is zero.
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