Download 1. The current in the secondary coil of a step

* 1. The current in the secondary coil of a step-up transformer is 1.25 A when the current in the primary
coil is 0.30 A. Determine the turns ratio, Ns/Np, of the transformer.
* A. 0.18
* B. 5.6
* C. 0.12
* D. 0.24
* E. 4.2
* 2. The current in a solenoid is decreased to one-half of its original value. Which one of the following
statements is true concerning the self-inductance of the solenoid?
* A. The self-inductance increases by a factor of four
* B. The self-inductance does not change
* C. The self-inductance increases by a factor of two
* D. The self-inductance decreases by a factor of two
* E. The self-inductance decreases by a factor of four
* 3. A transformer has 450 turns in its primary coil and 30 turns in its secondary coil. Which one of the
following statements concerning this transformer is true?
* A. This is a step-up transformer
* B. The power delivered to the secondary must be the same as that delivered to the primary
* C. The turns ratio is 15 for this transformer
* D. The ratio of the voltages Vs/Vp is 15 for this transformer
* E. The ratio of the currents Is/Ip is 0.067 for this transformer
* 4. A long, straight wire is in the same plane as a rectangular, conducting loop. The wire carries a
constant current I as shown in the figure. Which one of the following statements is true if the wire is
suddenly moved the loop?
If you cant do this one without the illustration, dont worry about it. Its just a rectangle with a line that
runs parallel about an in under it.
* A. There will be no induced emf and no induced current.
* B. There will be an induced current that is clockwise around the loop.
* C. There will be an induced emf, but no induced current.
* D. There will be an induced current that is counterclockwise around the loop.
* E. There will be an induced electric field that is clockwise around the loop.
* 5. Which one of the following statements best explains why semiconductors in transistors are doped?
* A. Doping makes the semiconducting materials non-conducting.
* B. Doping makes the charge carriers mobile.
* C. Doping converts the semiconducting materials into a metallic material like copper.
* D. Doping makes the charge carriers immobile.
* E. Doping changes the conductive properties of the semiconductors
* 6. A variable inductor is connected to an ac source. What effect does increasing the inductance have
on the reactance and current in this circuit?
* A. Reactance decreases, Current decreases
* B. Reactance no change, Current no change
* C. Reactance increases, Current increases
* D. Reactance decreases, Current decreases
* E. Reactance increases, Current decreases
* 7. When the frequency of an ac circuit is decreased, the current in the circuit increases. Which
combination of elements is most likely to comprise the circuit?
* A. Inductors only
* B. Resistors only
* C. Capacitors and resistors
* D. Capacitors only
* E. Inductors and capacitors
* 8. An incandescent light bulb radiates uniformly in all directions with a total average power of 100 W.
What is the maximum value of the magnetic field at a distance of .50 m from the bulb? [ Note 10 -7
means ten raised to the -7 power]
* A. Zero tesia
* B. 8.4 x 10-7 T
* C. 1.6 x 10-7 T
* D. 3.1 x 10-7 T
* E. 5.2 x 10-7 T
* 9. Which one of the following statements concerning diodes is false?
* A. A diode connected to an ac source allows current to flow only in one direction.
* B. A diode is fabricated by forming junctions between on n-type and two p-type semiconductors or on
p-type and two n-type semiconductors.
* C. A battery can be connected to a diode so that a continual flow of charge results.
* D. At an n-p junction in a diode that is not connected to a battery, an electric field exists across the
junction.
* E. Holes move in a diode under a forward-bias condition
* 10. Two series RCL circuits have the same resonant frequency. Circuit A has an inductance of 0.55 H
and circuit B has an inductance of .15H. Determine the ratio of the capacitance of the circuits, CA/CB/
* A. .27
* B. 3.7
* C. 2.4
* D. .44
* E. 1.8
* 11. An ac circuit consists of a series combination of an inductor and a capacitor. What is the phase
angle between the voltages across these two circuit elements?
* A. 270 degrees
* B. 90 deg.
* C. 360 deg.
* D. 180 deg.
* E. 0 deg.
* 12. What is the capacitive reactance of a circuit comprised of a 65.-uf capacitor and a 50.0-Hz
generator?
* A. 49 ohms
* B. 308 ohms
* C. 145 ohms
* D. 97.6 ohms
* E. 72.5 ohms
* 13. The current in a certain ac circuit is independent of the frequency at a given voltage. Which
combination of elements is most likely to comprise the circuit?
* A. A combination of inductors and resistors
* B. Resistors only
* C. Inductors only
* D. Capacitors only
* E. A combination of inductors and capacitors
* 14. In 1980, a television station began broadcasting on channel 32 at a frequency of 582 MHz. The
circuit contains an inductor with an inductance L= 4.15 x 10^-4 H and a variable-capacitance C.
Determine the value of C that allows this television station to be tuned in.
* A. 1.80 x 10^-16 F
* B. 3.61 x 10^-11 F
* C. 5.84 x 10^-12 F
* D. 1.10 x 10^-11 F
* E. 2.92 x 10^-12 F
* 15. A minivan moving at 38 m/s passes an unmarked state police car moving at 24 m/s. The
electromagnetic waves produced by the radar gun in the police car have a frequency of 8.25 x 109 Hz.
What is the magnitude of the difference in frequency between the waves emitted by the gun and those
that are reflected back from the speeding minivan?
* A. 770 Hz
* B. 2100 Hz
* C. 180 Hz
* D. 390 Hz
* E. 1440 Hz
* 16. Two polarizing sheets have their transmission axes parallel so that the intensity of unpolarized light
transmitted through both of them is a maximum. Through what angle must either sheet be rotated if
the transmitted intensity is 25 % of the incident intensity?
* A. 30 deg
* B. 15 deg
* C. 75 deg
* D. 60 deg
* E. 45 deg
* 17. A 0.45-m metal rod moves .11 m in a direction that is perpendicular to a 0.80-T magnetic field in an
elapsed time of 0.036 s. Assuming that the acceleration of the rod is zero m/s2, determine the emf that
exists between the ends of the rod.
* A. 9.1 x 10^-5 V
* B. 0.076 V
* C. 1.1 V
* D. This cannot be determined without knowing the orientation of the rod relative to the magnetic
field.
* E. .27 V
* 18. A series RCL circuit contains a 222-ohm resistor, a 1.40-uF capacitor, and a 0.125-H inductor. The
360-Hz ac generator in the circuit has an rms voltage of 208 V. What is the average electric power
dissipated by the circuit?
* A. 166 W
* B. 193 W
* C. 102 W
* D. 81 W
* E. 22 W
* 19. When the frequency of an ac circuit is increased at constant voltage, the current increases and
then decreases. Which combination of elements is most likely to comprise this circuit?
* A. A combination of inductors and capacitors
* B. Inductors only
* C. A combination of inductors and resistors
* D. Resistors only
* E. Capacitors only