Tutorial 12 A Self Test


1.   Complete these sentences.

A perfect inductor has ________________ resistance, but real inductors have a resistance. 


We model this as a ____________ _____________ in _____________ with a resistor.


As the frequency increases, the ____________________ of the inductor increases.


The voltage across the resistor is ___ _______________ with the current.  The current in the inductor leads/lags the voltage by __________ degrees.



2.      Draw a phasor diagram to show the phase relationships between the voltage and the currents in a parallel RL circuit that has a perfect inductor.


3.      A student works out the impedance of a parallel RL circuit using the equation:


         Discuss whether this is correct.



4.      Starting from the vector addition of currents in a parallel RL circuit, derive an equation for the impedance of the circuit.





5.      Calculate the overall impedance of this circuit, if the frequency is 20 Hz.