By Sam Wilson, CET
1. Which of the following could be used to make a Class A amplifier?
A.) SCR
B.) UJT
C.) LAD
D.) (None of these choices is correct.)
2. When a switching transistor is used in a switching circuit, its base -collector junction is A.) forward biased when in the on condition.
B.) reverse biased when in the on condition.
3. A 10,000 ohms-per-volt meter is used to measure a voltage of 3V.
Its resistance is
A.) 30,000 ohm.
B.) 3 ohm.
C.) unknown.
4. Which of the following is used to determine if an electrolytic capacitor is OK?
A.) BSR B.) VSR C.) ESR D.) VHR
5. A graph showing amplifier out put for various frequencies is called a
A.) log, log, deci-trig graph.
B.) Bode plot.
C.) 1/f graph.
D.) gain/slope path.
6. In a microprocessor, simple addition and subtraction is performed in the
A.) ALU.
B.) BFO.
C.) accumulator.
7. The circuit in Figure 1 is
A.) a bridge rectifier.
B.) a voltage doubler.
C.) a voltage tripler.
D.) (None of these choices is correct.)
8. Is the following statement correct? When you double the capacity, the capacitive reactance is halved.
A.) The statement is correct.
B.) The statement is not correct.
9. For the static-switch circuit of Figure 2, L and C are used as a
A.) snubber.
B.) commutator.
C.) filter.
D.) tuner.
10. To reverse the direction of rotation of a do shunt motor,
A.) reverse only the field connection.
B.) reverse the field and armature connection.
Fig. 1, 2
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ANSWERS
1. D. SCRs and UJTs are thyristors. An LAD is a light activated diode. None of these can be used to make a Class A amplifier.
2. A. When used as an amplifier, the base -collector junction is reverse biased.
3. C. The resistance of the voltmeter cannot be obtained from the information given.
4. C. ESR stands for equivalent series resistance of a capacitor. As an electrolytic capacitor ages, its ESR value increases.
5. B. The bode plot also is used to show amplifier phase shift vs. frequency. An interesting letter to the author was printed in the December 1986 Feedback column.
In this letter Ray Ketchledge discusses the origins of the bode plot.
6. A. Addition and subtraction is performed in the ALU (arithmetic logic unit). A microprocessor does not have a beat -frequency oscillator (BFO) or a discriminator.
7. D. The circuit in Figure 1 is known as a short circuit. Trace the closed loop around the outside of the circuit.
8. B. Although it is true that in creasing the capacitance decreases the capacitive reactance, the two values are not reciprocals.
9. B. A commutator is used to shut off an SCR. The SCR will stop conducting when its current is equal in magnitude, but opposite in direction, to the LC -tuned circuit.
Actually, the charged capacitor in the tuned circuit tries to discharge in the anode -to -cathode direction through the SCR.
10. A. You could reverse either the field connection or the armature connection to reverse the direction of rotation. However, if you reverse both, the direction of rotation will not change.
Also see: What do you know about electronics? -- Living with models
Circuit analysis and troubleshooting quiz