600 final

600 final Questions And Answers Verified 100% A 1.5 volt 8 milliamp light emitting diode needs to be operated from a 24VDC circuit. What series resistance is required? - 3k ohms A brake coil has an inductance off 4 Henries - A string of temporary lighting has fifteen 100 watt light bulbs. A 15 amp breaker is the max size that can be used with the 14 gauge wire used in this 120 volt circuit. What is the current? - 12.5 A An elevators motor rotates at 1200 rpm at contract speed and is geared at a ratio of 40:1. If the motor turns 40 rpm the sheave turns 1 rpm. What is the actual speed of the drive sheave in rpms? - 30 rpm An MOV placed around a relay coil for voltage spike suppression has shorted. What would the effects be? - Spike suppression would be lost For a NPN transistor to be properly biased, which of the following must be true? - The base emitter conjunction must be forward biased. How can pitting due to arcing be reduced on relay contact surfaces? - Placing a capacitor and resistor in parallel with the load. How long will it take for this capacitor to be considered fully charged? - 5 Seconds How many rectifier diodes are required to make a full wave bridge rectifier? - 4 If a circuit has three inductors in parallel of 10, 15 and 20 henries, what is the total inductance? - 4.61 Henries In elevator systems, what do noise suppression capacitors help reduce? - Voltage spikes On the fourteen pin DIP IC shown in figure 4 what is the location of pin 14? - Top right Refer to figure, If load resistance R2 is reduced by half, what happens to the zener diode? - Zener current will decrease Refer to figure, What inputs are necessary to get a low (0) on the output? - A low (0) on input A and B Refer to the figure, for the comparator circuit shown, what will happen to the output if the non inverting input goes more positive than the inverting input? - The output will go to zero. Refer to the figure, for the inverting op amp shown, what is the output voltage? - 25 mv Refer to the figure, the zener diode is designed to breakdown at 6VDC. What is the voltage drop across resistor 1, with a constant DC supply of 10 VDC? - 4V Refer to the figure, what inputs are necessary to get a high (1) on the output? - A high (1) on input A and B The entire cab assembly, including the car sling, cab doors, operator, etc., weighs 3400 lbs. The capacity of the elevator is 2500 lbs. The car must be counterweighted at 40% of the capacity plus the weigh of the car assembly. What is the weight of the counterweight assembly? - 4400 lbs The photodiode will conduct current when it detects? - Light The secondary load current of a 2300 to 120 volt transformer is 46 amperes. What is the current in the primary? - 2.4 Amps The voltage required to cause conduction across the junction in a geranium diode is? - 0.3 What combination of capacitors could be used to replace a 100 uf/250VDC capacitor? - 2-50uf/300vdc capacitors in parallel What does the circuit in figure 5 represent? - A relay timer What does the symbol in figure 6 represent? - LED What does the symbol shown below represent? - An SCR What effect does the counter electromotive force have in an inductive circuit? - It is an opposing force to the applied voltage which resists changes in circuit current What is the AC component of a DC power supply output called? - Ripple voltage What is the binary equivalent of 131 to the 10th power? - What is the correct average output voltage for a full-wave bridge rectifier using silicon diodes with a power supply voltage of 300 VAC? - 190 VDC What is the hexadecimal equivalent of to the 2nd power? - 5AD What is the length of time required to charge. 500 microfarad capacitor in series with a 10k ohm resistor to the max applied voltage of 125 VDC? - 5 Seconds. 500microfaradsX10kohmX5 What is the most important property an inductor possesses? - The ability to resist changes in current flow What is the peak value of an AC voltage whose RMS value is 120 volts? - 169.7 VAC What is the time constant for a circuit with 150k ohms and 2 microfarad capacitor? - 0.3 seconds What is the total capacitance and the max applied voltage for the circuit in the figure? - 350uf/150VDC What is usually done to protect large capacitors during charging? - A resistors placed in series with the capacitor.