Physics Electromagnetic Waves Level: High School
An electromagnetic wave has an electric field with peak value 250 N/C . What is the average intensity of the wave ?a. 0.66 W/m^2
b. 0.89 W/m^2
c. 83 W/m^2
d. 120 W/m^2
e. 170 W/m^2
Physics Ray Optics Level: High School
The average distance between the surface of the earth and the surface of the sun is 1.49 x 10^11 m. How much time , in minutes , does it takes for light leaving the surface of the sun to reach the earth ?a. Zero minutes .
b. 2.9 x 10^-3 minutes.
c. 8.3 minutes.
d. 74 minutes.
e. 500 minutes.
Physics Ray Optics Level: High School
When a radio telescope observes a region of space between two stars , it detects electromagnetic radiation that has a wavelength of 0.21 m . This radiation was emitted by hydrogen atoms in the gas and dust located in that region . What is the frequency of this radiation ?a. 7.1 x 10^10 Hz
b. 2.1 x 10^14 Hz
c. 3.0 x 10^8 Hz
d. 6.9 x 10^11 Hz
e. 1.4 x 10^9 Hz
Physics Ray Optics Level: High School
Complete the following sentence . The various colors of visible light differ ina. Frequency only.
b. Wavelength only.
c. Their speeds in a vacuum.
d. Frequency and wavelength.
e. Frequency and their speed in a vacuum.
Physics Alternating Current Level: High School
A television station broadcasts at a frequency of 86 MHz . The circuit contains an inductor with an inductance L = 1.2 x 10^-6 H and a variable capacitance C . Determine the value of C that allows this television station to be turned in .a. 2.9 x 10^-12 F
b. 5.8 x 10^-12 F
c. 1.8 x 10^-11 F
d. 3.6 x 10^-11 F
e. 1.1 x 10^-10 F
Physics Alternating Current Level: High School
Semi conductors
Which one of the following statements concerning diodes is false ?a. A diode is fabricated by forming junctions between one n-type and two p-type semi-conductors or one p-type and two n-type semi-conductors .
b. At an n-p junction in a diode that is not connected to a battery , an electric field exists across the junction.
c. A battery can be connected to a diode so that a continual flow of charge results.
d. A diode connected to an ac source allows current to flow only in one direction.
e. Holes move in a diode under a forward-bias condition .
Physics Alternating Current Level: High School
Which one of the following statement best explains why semiconductors in transistors are doped ? a. Doping makes the charge carries mobile . b. Doping makes the charge carriers immobile. c. Doping make the semi-conducting materials non-conducting. d. Doing changes the conductive properties of the semi-conductors. e. Doping converts the semi-conducting materials into a metallic material like copper.Physics Alternating Current Level: High School
The graph at “click here” shows the impedance as a function of frequency for a series RCL circuit . At what frequency does the capacitor make the larges contribution ?a. f1
b. f2
c.f3
d. f1 or f3
e. f1 or f2 or f3
Physics Alternating Current Level: High School
An ac generator supplies an rms (not peak) voltage of 180 V at 60.0 Hz . Determine the peak voltage of the generator .a. 180 V
b. 255 V
c. 300 V
d. 360 V
e. 480 V
Physics Alternating Current Level: High School
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. Resistors only.
b. Inductors only.
c. Capacitors only.
d. A combination of inductors and resistors.
e. A combination of inductors and capacitors.
Physics Alternating Current Level: High School
An ac voltage source that has a frequency f is connected across the ends of an inductor . Which one of the following statements correctly indicates the effect on the inductive reactance when the frequency is increases to 2 f ?a. The inductive reactance increases by a factor of two.
b. The inductive reactance increases by a factor of four.
c. The inductive reactance is unchanged .
d. The inductive reactance decreases by a factor or four.
e. The inductive reactance decreases by a factor of two.
Physics Alternating Current Level: High School
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. Resistors only.
b. Inductors only.
c. Capacitors only.
d. Capacitors and resistors .
e. Inductors and capacitors.
Physics Alternating Current Level: High School
What is the capacitive reactance of a circuit comprised of a 65.0 micro F capacitor and a 50.0 Hz generator ?a. 49.0 ohm
b. 72.5 ohm
c. 97.6 ohm
d. 145 ohm
e. 308 ohm
Physics Alternating Current Level: High School
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. Resistors only.
b. Inductors only.
c. Capacitors only.
d. A combination of inductors and resistors .
e. A combination of inductors and capacitors.
Physics Force & Laws Of Motion Level: High School
How long does it take an automobile traveling in the jett lane at 60.0 km/h to pull alongside a car traveling in the same direction in the right lane at 40.0 km/h if the car’s front bumpers are initially 100 m apart ?