600 Test Questions

Front 1

The photo diode would conduct current when it detects

Back 1

Light

Front 2

What is this graphic

Back 2

A relay timer

Front 3

If a circuit has three inductors in parallel of 10, 15, 20 Henry's, what is the total inductance?

Back 3

4.61 henries

Front 4

What is this symbol

Back 4

LED light emitting diode

Front 5

When testing transistors

Back 5

A .7 drop from base to emitter is an indication of a good junction

Front 6

What symbol is this

Back 6

SCR

Front 7

What factors determines the voltage rating of a capacitor?

Back 7

The dielectric

Front 8

What is usually done to protect large capacitors during charging

Back 8

A resistor is placed in series with the capacitor

Front 9

What do you need to be aware of when using electrolytic capacitors

Back 9

They may be popularity sensitive

Front 10

Why are bleeder resistors sometimes connected across high voltage capacitors

Back 10

To help drain voltage when power is removed

Front 11

What effect does counter electromotive force (CEMF) have in an inductive circuit

Back 11

It is an opposing force to the applied voltage which resist changes in circuit

Front 12

What is the time constant for a circuit with 150k ohms and 2 micro farad capacitor

Back 12

(.3 seconds) R×C. 150000×2×10 to the 6th

Front 13

How long will it take for the capacitor to be fully charged

Back 13

1.5 seconds

Front 14

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

Back 14

1507 ohms. XL=2pieFL. 6.28×60hz×4henerys = 1507

Front 15

What's the voltage required to cause conduction across the junction in a germanium and silicon diode

Back 15

.3 germanium

.7 silicon

Front 16

When DC is first applied in an AC circut

Back 16

Capacitor voltage is minimum and current is maximum

Front 17

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

Back 17

30 rpm

Front 18

When removing, installing. And handling solid state circuit boards what precautions should be taken

Back 18

Remove power and wear a wrist ground strap

Front 19

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

Back 19

12.5 Amp. P=I×E. 15(100)/120=I

Front 20

What is the peak value of an AC voltage whose RMS value is 120 volts

Back 20

169.7 VAC. 120×1.414

Front 21

What is the binary equivalent of 131

Back 21

1000 0011.

Front 22

What inputs are necessary to get a high (1) on the output of an AND gate

Back 22

A high on input A and low (0) on input B

A high (1) on input A and B

Front 23

What is the hexadecimal equivalent of 0101 1010 1101

Back 23

5AD

Front 24

A low (0) on input A and a High (1) on input B

Back 24

.

Front 25

What is the total capacitance and the maximum applied voltage for the circuit in figure 5

Back 25

350uf/250VDC

Front 26

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

Back 26

25 seconds. Tc=R×C. 10,000×.0005=5secs×5

Front 27

How can pitting due to arching be reduced on relay contact surface

Back 27

Placing a capacitor and resistor in series with the contacts

Front 28

An elevator system, what does noise suppression capacitors help reduce

Back 28

Voltage spikes

Front 29

What combination of capacitors could be used to replace a 100uf/250VDC capacitor

Back 29

2-50uf/300VDC capacitor in parallel

Front 30

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.

Back 30

4400 lbs. 3400+(2500×.4)=4400

Front 31

What is the correct average output voltage for a full wave bridge rectifier using silicone diodes with a peak input supply voltage of 300VAC

Back 31

190VDC. 300×.636=190.8-.7

Front 32

A 1.5v 8 milliamp light emitting diode needs to be operated from a 24VDC circuit. What series resistance is required.

Back 32

3k ohms. E=IR

Front 33

For NPN transistor to be properly biased, which of the following must be true

Back 33

Both A and B

The base-emitter junction must be forward biased

The base and collector junction must be reverse biased

Front 34

What is correct about collector current of a transistor

Back 34

It is nearly equal to the emitter current

Front 35

When is CEMF greatest for an inductor in an AC circuit

Back 35

When current is changing rapidly

Front 36

What is the most important property an inductor possesses

Back 36

The ability to resist changes in current flow

Front 37

What is correct regarding capacitors

Back 37

Placing 2 capacitors in series decreases the capacitance

Front 38

What is correct about a forward biased silicon diode

Back 38

The anode is .7 volts higher then the cathode

Front 39

How many rectifier diodes are required to make a full wave bridge rectifier

Back 39

4

Front 40

What is the limit of magnetic strength around an inductor even though the current through the coil increases

Back 40

Saturation

Front 41

How is an SCR turned off

Back 41

Voltage is removed anode to cathode

Front 42

What is the AC component of a DC power supply output called

Back 42

Ripple voltage

Front 43

Why are DC power supply series regulators are better then shunt regulators

Back 43

The operate more accurately over a greater current and voltage range

Front 44

An MOV placed around a relay coil for voltage spike suppression has shorted what would the effects be

Back 44

Spike suppression would be lost

Front 45

Figure 6. Load resistance R2

Back 45

Zenner current will decrease

Front 46

A properly biased SCR to turn on

Back 46

Anode positive, cathode negative, gate pulse positive

Front 47

Figure 7

Back 47

The output will saturate in the positive direction