A circuit is shown in the diagram and the measurments of its

A circuit is shown in the diagram, and the measurments of its driving emf e and current I are plotted. Is the circuit capacitive, inductive, or resonant? Estimate the value of R.

Solution

I leads V by pi/3.

phase angle = - pi/3

that means circuit is capacitive.

b) phase angle = tan^-1( (XL - Xc) / R ) = - pi/3

Xc - XL   / R = tan (pi/3)

Xc - XL = 1.732R

impedance, Z = sqrt[ R^2 + (XL -XC)^2 ] = sqrt[ R^2 + (1.732R)^2 ]

Z = 2R

Imax = Vmax / Z

0.05 = 28 / 2R

R = 280 ohm