Chapter 24: Alternating Current Circuits
MCAT Study Guide




1.  

The following information pertains to questions 1-4.

In the circuit at the right, an ac power supply is connected to the series combination of a resistor with resistance R and an ideal (zero resistance and impedance) ac ammeter which measures the "effective" current flowing in the circuit. An ac voltmeter which measures "effective" voltage is wired in parallel with the resistor. The instantaneous output voltage of the power supply varies with time according to
v(t) = Vm sin(o t)
and the instantaneous ac current at any point in the circuit varies with time according to
i(t) = Im sin(' t - ).
The ammeter and voltmeter read Io and Vo respectively.

The two frequencies, o and ', are such that o is ___ '.

equal to
less than
more than
incomparable, without additional information, with


2.  

The phase angle is ___ o.

O
+45
-45
+90
-90
some other value


3.  

The effective current flowing in the circuit, Io, is Im x ___.

1
1/2
2
1/2
2
some other value


4.  

If the amplitude of the output voltage of the power supply was increased slightly, Io would ___.

increase
decrease
remain constant
be impossible to predict


5.  

The following information pertains to questions 5-7.

In the circuit at the right, an ac power supply is connected to the series combination of a capacitor with capacitance C and an ideal ac ammeter which measures the "effective" current flowing in the circuit. An ac voltmeter which measures "effective" voltage is wired in parallel with the capacitor. The instantaneous output voltage of the power supply varies with time according to
v(t) = Vm sin(o t)
and the instantaneous ac current at any point in the circuit varies with time according to
i(t) = Im sin(' t - ).
The ammeter and voltmeter read Io and Vo respectively.

The two frequencies, o and ', are such that o is ___ '.

equal to
less than
more than
incomparable, without additional information, with


6.  

The effective voltage across the capacitor, Vo, is Vm x ___.

1
1/2
2
1/2
2
some other value


7.  

If the capacitance of the capacitor, C, was increased slightly, Io would ___.

increase
decrease
remain constant
be impossible to predict


8.  

The following information pertains to questions 8-10.

In the circuit at the right, an ac power supply is connected to the series combination of an inductor with inductance L and an ideal ac ammeter which measures the "effective" current flowing in the circuit. An ac voltmeter which measures "effective" voltage is wired in parallel with the inductor. The instantaneous output voltage of the power supply varies with time according to
v(t) = Vm sin(o t)
and the instantaneous ac current at any point in the circuit varies with time according to
i(t) = Im sin(' t - ).
The ammeter and voltmeter read Io and Vo respectively.

The two frequencies, o and ', are such that o is ___ '.

equal to
less than
more than
incomparable, without additional information, with


9.  

If the inductance of the inductor, L, was increased slightly, Io would ___.

increase
decrease
remain constant
be impossible to predict


10.  

If the inductance of the inductor, L, was increased slightly, the ratio, Vo/Io would ___.

increase
decrease
remain constant
be impossible to predict


11.  

The following information pertains to questions 26-29.

Refer to the figure at the right. A variable resistor with initial resistance Ro, a capacitor with capacitance Co and a pure variable inductor with initial inductance Lo are connected in series and then the series combination is connected to the output of an ac power supply with an effective output voltage Vo at a frequency o well above the resonant frequency of the circuit.

The effective voltage across the inductor is ___ the effective voltage across the capacitor.

equal to
more than
less than
incomparable, without additional information, with


12.  

If the resistance of the resistor was increased slightly, the resonant frequency of the circuit would ___.

increase
decrease
remain constant
be impossible to predict


13.  

If the inductance of the inductor was increased slightly, the resonant frequency of the circuit would ___.

remain constant
increase
decrease
be impossible to predict


14.  

If the frequency of the output voltage of the power supply was increased slightly, the impedance of the circuit would ___.

remain constant
increase
decrease
be impossible to predict


15.  

The following information pertains to questions 15-17.

The figure at the right shows one cycle of an alternating voltage.

The period of this ac voltage is ___ s.

0.25
0.5
0.75
1.0
1.5
2.0


16.  

If this ac voltage was connected to a particular resistor with resistance Ro, heat would be created within the resistor at an average rate Po. If this same resistor was connected to a dc voltage source and heat was created within the resistor at the same constant rate Po, the output voltage of this dc power source would have to be ___ V.

1
2.0
5.0
7.07
10


17.  

If this ac voltage was connected to a particular resistor with resistance Ro, and an ac voltmeter was used to measure the "effective voltage" across the resistor, the voltmeter would read ___ V.

1
2.0
5.0
7.07
10


18.  

The following information pertains to questions 18 and 19.

In the figure at the right, one cycle of a sinusoidal voltage is plotted as a function of time. The equation which describes the voltage is

v(t) = Vosin (2f t).

In the above equation described by the curve in the figure, the numerical value for the parameter Vo is _____ volts.

7.1
-7.1
10
14
-14
20


19.  

In the above equation, the numerical value of the parameter f is _____ Hz.

0.1
0.2
0.25
0.5
1.0


Bosworth et al, ARCO MCAT SuperCourse (MacMillan, 1997). Copyright 1997, 1996, 1994, 1991 by Stefan Bosworth, Ronald Drucker, Edgar Schnebel, Denise Garlan, Rosie Soy and Marion Brisk. Used by permission of MacMillan, Inc.

For more information, go to http://www.amazon.com.

The Virtual Prof's Physics Study Guide for the MCAT. Copyright 1997 by Glen Terrell and RonJon Publishing, Inc. Used by permission of Glen Terrell. For more information, go to http://www.virtualprof.com.


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