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47 Cards in this Set
- Front
- Back
The photo diode would conduct current when it detects |
Light |
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What is this graphic |
A relay timer |
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If a circuit has three inductors in parallel of 10, 15, 20 Henry's, what is the total inductance? |
4.61 henries |
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What is this symbol |
LED light emitting diode |
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When testing transistors |
A .7 drop from base to emitter is an indication of a good junction |
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What symbol is this |
SCR |
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What factors determines the voltage rating of a capacitor? |
The dielectric |
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What is usually done to protect large capacitors during charging |
A resistor is placed in series with the capacitor |
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What do you need to be aware of when using electrolytic capacitors |
They may be popularity sensitive |
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Why are bleeder resistors sometimes connected across high voltage capacitors |
To help drain voltage when power is removed |
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What effect does counter electromotive force (CEMF) have in an inductive circuit |
It is an opposing force to the applied voltage which resist changes in circuit |
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What is the time constant for a circuit with 150k ohms and 2 micro farad capacitor |
(.3 seconds) R×C. 150000×2×10 to the 6th |
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How long will it take for the capacitor to be fully charged |
1.5 seconds |
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A brake coil has an inductance of 4 henrys. If the coil was placed into a circuit with an operating frequency of 60hz would have a inductance of |
1507 ohms. XL=2pieFL. 6.28×60hz×4henerys = 1507 |
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What's the voltage required to cause conduction across the junction in a germanium and silicon diode |
.3 germanium .7 silicon |
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When DC is first applied in an AC circut |
Capacitor voltage is minimum and current is maximum |
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An elevator motor rotates at 1200 rpm at contract speed and is geared at a ratio of 40:1. If the motor turns 40rpm. And turns 1rpm. What's the actual speed of the drive sheave in rpm |
30 rpm |
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When removing, installing. And handling solid state circuit boards what precautions should be taken |
Remove power and wear a wrist ground strap |
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A string of temporary lighting has fifteen 100watt bulbs. A 15amp breaker is the maximum size that can be used. 120volt circuit. What is the current |
12.5 Amp. P=I×E. 15(100)/120=I |
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What is the peak value of an AC voltage whose RMS value is 120 volts |
169.7 VAC. 120×1.414 |
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What is the binary equivalent of 131 |
1000 0011. |
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What inputs are necessary to get a high (1) on the output of an AND gate |
A high on input A and low (0) on input B A high (1) on input A and B |
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What is the hexadecimal equivalent of 0101 1010 1101 |
5AD |
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A low (0) on input A and a High (1) on input B |
. |
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What is the total capacitance and the maximum applied voltage for the circuit in figure 5 |
350uf/250VDC |
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What is the length of time required to charge a 500-microfarad capacitor in series with a 10k ohm resistor. Maximum applied voltage of 125VDC |
25 seconds. Tc=R×C. 10,000×.0005=5secs×5 |
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How can pitting due to arching be reduced on relay contact surface |
Placing a capacitor and resistor in series with the contacts |
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An elevator system, what does noise suppression capacitors help reduce |
Voltage spikes |
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What combination of capacitors could be used to replace a 100uf/250VDC capacitor |
2-50uf/300VDC capacitor in parallel |
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The entire cab assembly, including the car sling cab doors operator etc weighs 3400lbs. The capacity of the elevator is 2500 lbs. The car must be counter weighted at 40% of capacity plus the weight of the car assembly. What is the weight of the counterweight assembly. |
4400 lbs. 3400+(2500×.4)=4400 |
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What is the correct average output voltage for a full wave bridge rectifier using silicone diodes with a peak input supply voltage of 300VAC |
190VDC. 300×.636=190.8-.7 |
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A 1.5v 8 milliamp light emitting diode needs to be operated from a 24VDC circuit. What series resistance is required. |
3k ohms. E=IR |
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For NPN transistor to be properly biased, which of the following must be true |
Both A and B The base-emitter junction must be forward biased The base and collector junction must be reverse biased |
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What is correct about collector current of a transistor |
It is nearly equal to the emitter current |
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When is CEMF greatest for an inductor in an AC circuit |
When current is changing rapidly |
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What is the most important property an inductor possesses |
The ability to resist changes in current flow |
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What is correct regarding capacitors |
Placing 2 capacitors in series decreases the capacitance |
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What is correct about a forward biased silicon diode |
The anode is .7 volts higher then the cathode |
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How many rectifier diodes are required to make a full wave bridge rectifier |
4 |
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What is the limit of magnetic strength around an inductor even though the current through the coil increases |
Saturation |
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How is an SCR turned off |
Voltage is removed anode to cathode |
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What is the AC component of a DC power supply output called |
Ripple voltage |
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Why are DC power supply series regulators are better then shunt regulators |
The operate more accurately over a greater current and voltage range |
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An MOV placed around a relay coil for voltage spike suppression has shorted what would the effects be |
Spike suppression would be lost |
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Figure 6. Load resistance R2 |
Zenner current will decrease |
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A properly biased SCR to turn on |
Anode positive, cathode negative, gate pulse positive |
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Figure 7 |
The output will saturate in the positive direction |