1. A transformer has a primary voltage of 115 V and a secondary voltage of 24 V. If the number of turns in the primary is 345, how many turns are in the secondary?
A. 8
B. 690
C. 72
D. 1,653
2. To use your left hand to determine the direction of the voltage developed in a moving conductor in a stationary magnetic field, you must point your
A. forefinger in the direction of the lines of force.
B. thumb in the direction of the electromagnetic force.
C. thumb in the direction of the magnetic flux.
D. forefinger in the direction of the motion.
3. In a cathode ray tube, the number of electrons that reach the fluorescent screen is controlled by the
A. cathode.
B. grid.
C. anode.
D. deflecting plate.
4. Electrons are emitted from a conductor when the conductor is
A. bombarded by high-speed electrons.
B. subjected to a small voltage.
C. exposed to weak light.
D. cooled rapidly.
5. If an electrically uncharged body is contacted by an electrically charged body, the uncharged body will
A. develop the same charge as the charged body.
B. neutralize the charged body.
C. remain a neutrally charged body.
D. develop the opposite charge as the charged body.
6. An electric heating element is connected to a 110 V circuit and a current of 3.2 A is flowing through the element. How much energy is used up during a period of 5 hours by the element?
A. 1,760 Wh
B. 352 Wh
C. 550 Wh
D. 2,580 Wh
7. A transmission system at a radio station uses a/an _______ to convert a direct current into a high frequency alternating current.
A. modulator
B. demodulator
C. oscillator
D. transmitting antenna
8. The magnitude of the voltage induced in a conductor moving through a stationary magnetic field depends on the _______ and the _______ of the conductor.
A. length, speed
B. color, capacitance
C. distance, circumference
D. resistance, current
9. If the resistance of an electric circuit is 12 ohms and the voltage in the circuit is 60 V, the current flowing through the circuit is
A. 0.2 A.
B. 5 A.
C. 720 A.
D. 60 A.
10. What bias conditions must be present for the normal operation of a transistor amplifier?
A. Both junctions must be reverse biased.
B. Both junctions must be forward biased.
C. The emitter-base junction must be forward biased, and the collector-base junction must be reverse biased.
D. The emitter-base junction must be reverse biased, and the collector-base junction must be forward biased.
11. A circuit contains two devices that are connected in parallel. If the resistance of one of these devices is 12 ohms and the resistance of the other device is 4 ohms, the total resistance of the two devices is
A. 16 ohms.
B. 0.333 ohms.
C. 0.0625 ohms.
D. 3 ohms.
12. Including a full-wave rectifier in an AC circuit will yield a(n) _______ current.
A. intermittent alternating
B. continuous direct
C. continuous alternating
D. intermittent direct
13. If one body is positively charged and another body is negatively charged, free electrons tend to
A. move from the positively charged body to the negatively charged body.
B. remain in the positively charged body.
C. remain in the negatively charged body.
D. move from the negatively charged body to the positively charged body.
14. Which of the following does not affect the electrical resistance of a body?
A. Material composing the body
B. Temperature of the body
C. Length of the body
D. Bodies directly surrounding the body
15. The grid in a high-vacuum triode is usually kept negatively charged with respect to the cathode so that the electrons may be
A. attracted to the cathode instead of the grid.
B. attracted to the anode instead of the grid.
C. accelerated toward the cathode.
D. accelerated toward the anode.
16. The relationship between a cathode and an anode involves
A. electrons.
B. diodes.
C. neutrons.
D. protons.
17. The available source of charge that pushes a charge through a circuit is
A. resistance.
B. voltage.
C. direct current.
D. alternating current.
18. An example of an atom that has no charge is one that has
A. 2 protons, 2 electrons, and 1 neutron.
B. 3 protons, 2 electrons, and 1 neutron.
C. 3 protons, 1 electron, and 3 neutrons.
D. 1 proton, 2 electrons, and 3 neutrons.
19. Suppose that you're facing a straight current-carrying conductor, and the current is flowing toward you. The lines of magnetic force at any point in the magnetic field will act in
A. the same direction as the current.
B. the direction opposite to the current.
C. a clockwise direction.
D. a counterclockwise direction.
20. The unit for measuring electric power is the
A. volt.
B. watt.
C. ampere.
D. ohm.
21. When an electric current flows through a long conductor, each free electron moves
A. through a relatively short distance.
B. from one end of the conductor to the other end.
C. back and forth between the ends of the conductor.
D. with a speed of 300,000,000 m/s.
22. A unit for measuring frequency is the
A. hertz.
B. ohm.
C. ampere.
D. watt.
23. When all parts of a circuit are composed of conducting materials, the circuit is said to be
A. closed.
B. parallel.
C. open.
D. shorted.
24. A PNP transistor is connected in a circuit so that the collector-base junction remains reverse biased and the emitter-base junction is forward biased. This transistor can be used as a power amplifier because
A. the output current will be much larger than the input current.
B. the output current will be much smaller than the input current.
C. the output voltage will be much smaller than the input voltage.
D. the output voltage will be much larger than the input voltage.
25. If a bar of copper is brought near a magnet, the copper bar will be
A. made into an induced magnet.
B. repelled by the magnet.
C. unaffected by the magnet.
D. attracted by the magnet.
1.C
2.A
3.B
4.A
5.A
6. A
7. C
8. A
9. B
10. C
11. D
12. B
13. D
14. D
15. B
16. A
17. B
18. A
19. C
20. B
21. A
22. A
23. A
24. D
25. C
15. A
19. D
Actually, CHILL...the correct answer for #15 is B, and the correct answer for #19 is C. My daughter just took this exam & she made a 100 on it.
1. To find the number of turns in the secondary of a transformer, we can use the turns ratio formula, which states that the ratio of the number of turns in the primary to the number of turns in the secondary is equal to the ratio of the voltages across the primary and secondary windings. So in this case, we have:
115V (primary voltage) / 24V (secondary voltage) = 345 turns (primary) / x turns (secondary)
To find the number of turns in the secondary, we can rearrange the formula and solve for x:
24V (secondary voltage) * 345 turns (primary) = 115V (primary voltage) * x turns (secondary)
Now we can calculate the value of x:
x = (24V * 345 turns) / 115V
x = 69 turns
Therefore, the number of turns in the secondary is 69, and the answer is option B.