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問題一覧
1
What is shown in the image below
Two Potentiometer symbols
2
What are potentiometers?
They’re basically resisters that have a dial or knob that allow you to change its resistance based on the position of the dial or knob.
3
What do the dots mean?
It means that the lines are supposed to be connected and they’re on the same conductive material.
4
What is shown. in the image below?
its an OP Amp
5
How can you use an IC’s datasheet and the circuit board schematic where it resides to help you find a specific pin?
- You find a specific pin by looking at other pins on the schematic to see what they’re connected to so that you have a point of reference to trace back to the desired pin.
6
Give an example of how you’d use other pins on an IC as a reference point to find a specific pin.
- If you’re looking for pin38 on the IC on the circuit board, then look on schematic for other pin numbers of that same IC and see what theyre close to. If you find that pin11 is on one side of a square shaped IC and is connected to another component that you can actually find on the circuit board, then remember the number of that pin and use the data sheet for that IC to help you trace back from pin11 to pin38.
7
If you see a component on a schematic that has a COM pin, what does that mean?
COM means that its connected ground. You can also tell that its ground because the line is thivker than other lines.
8
Are all components of a circuit directly connected to ground?
No, ground is only a reference point for voltage. sometimes, components like resistors and capacitors, have both of their leads connected to other active components(like motors and/or IC pins)
9
what the typical configuration of a bipolar transitor?
Pin1: Emmitter Pin2: Base Pin3: Collector
10
How can you use an IC’s datasheet and the circuit board schematic where it resides to help you find a specific pin?
You find a specific pin by looking at other pins on the schematic to see what they’re connected to so that you have a point of reference to trace back to the desired pin.
11
Typically, in a transistor, the collector current is higher than the base current.
True
12
What does the Current Gain tell you about a transistor?
It’s the ratio between the base current and the collector current.
13
whats the formula for Current Gain?
β = Collector Current/Base Current
14
When is current the same everywhere in a circuit and when can the current have different values throughout the circuit?
Current is the same everywhere in a series circuit Current can vary in parallel circuits.
15
When is voltage the same everywhere in a circuit and when can the volatge have different values throughout the circuit?
volatge is the same in parallel circuit volatge can be different in series circuits
16
Whats the main difference between NPN transistors and PNP transistors?
They’re direction of current flow is opposite
17
What do these symbols stand for and what dies the arwo indicate?
These are both symbols for transistors(NPN & PNP). The arrow shows the conventional direction of current. the conventional current flows into or out of the Emitter pin.
18
When measuring inductance and capacitance, why is it good to have short meter probe wires?
Because wires have an innate resistance and inductance. The longer the meter probe wires are, the more the innate inductance can throw off the measurement of the actual inductance of the inductor you’re measuring.
19
How can transformers step up and step down power?
If the secondary winding has more windings in it than the primary winding, then the induced current or voltage coming out of the secondary winding will be stepped up. The opposite is true if the secondary winding has less windings than the primary winding. The power will be stepped down.
20
How do the power companies step down the tens of thousands of voltages sent to the city’s residents from the power generation stations?
They use step down transformers where the secondary windings are less than the primary windings
21
What's a good superficial equation that you can use to help you step up and step down voltages through a transformer?
V₁(Primary Voltage)/V₂(Secondary Voltage) = N₁(Primary Turns)/N₂Secondary Turns)
22
Transformers only function with -
AC electricity
23
What's a good superficial equation that you can use to help you find the secondary coil’s voltage output and current output of a transformer?
Secondary Voltage: V₂=V₁*(N₁/N₂) Secondary Current: I₂=I₁*(N₁/N₂)
24
“N₁/N₂” is sometimes just called:“N₁/N₂” is sometimes just called:
n
25
A transformer stepped down 120V to 9V. To see how many times a step down transformer stepped down voltage, what do you do?
You divide the larger number by the smaller number. 120/9=13.3. The voltage was stepped down 13.3 times.
26
On a transformer, how do you know which wires are primary and which wires are secondary?
The top line “WHT-ORN 277V 60Hz”(White-Orange) is the primary wires and the second line “BLK-BLU 120V 25mA”(Black-Blue) is the secondary wires.
27
This transformer is mislabeled. The 3 wires are the secondary and the two wires on the other side are primary. On the side with 3 wires, What’s the middle red wire for?
The middle wire means this is a tapped transformer. The secondary coil/winding has the red middle wire coming out from the middle of the coil/winding so that you can get a different voltage or different turns ratio.
28
what is the reciprocal or inverse of a number?
flipping the numerator and denominator.(4=4/1=1/4)
29
how do you find the inverse of 17?
make it a fraction: 17=17/1 flip it: 1/17 solve it: 0.05
30
When you’re trying to find the primary voltage or secondary voltage of a transformer and you’ve calculated either the turns ratio or voltage ratio, when do you invert the ratio to find either the primary or secondary voltage?
When you’re trying to find the step-up voltage(from lower voltage to higher voltage) you multiply with the same ratio. When you’re trying to find the step-down voltage(from higher voltage to lower voltage) you multiply with the inverse of the ratio.
31
Let’s say you have a step down transformer that steps down 100V to 25V and you’ve applied 10V to the primary. The turns ratio is 4 to 1 What will the secondary voltage be? The formula is V₁/V₂=N₁/N₂.
Rearrange: V₂=V₁*N₁/N₂ Plug in: V₂=10*4/1 Inverse the ratio: V₂=10*¼ Solve: V₂= 2.5V
32
Let’s say you have a step up transformer that steps up 30V to 90V and you’ve applied 20V to the primary. The turns ratio is 3 to 1 What will the secondary voltage be? The formula is V₁/V₂=N₁/N₂.
Rearrange: V₂=V₁*N₁/N₂ Plug in: V₂=20*3/1 Solve: V₂= 60V
33
if youve pulled the insert of a component lead out of a circuit, how do safely push it back through the hole?
you heat up the solder thats around the insert and slowly push the lead back in with a small tool to prevent from touching the hot lead.
34
What are some of the various signals a signal generator could output?
Sine waves, square waves, ramp waves, pulse waves, and more.
35
How do you hook a component up to a signal generator for power application?
Take the + and - probes and connect them to the input leads or terminals on a component then connect the other end of the + and - probes and plug them into their corresponding sockets in the output channel(CH1 or CH2) of the signal generator
36
How do you hook a component up to an oscilloscope for measurement?
Take the + and - probes and connect them to the input and output leads or terminals on a component then connect the other end of the + and - probes and plug them into their corresponding sockets in the channel(CH1 or CH2) of the oscilloscope
37
How do you remove a lead or leads of a componet when you’re about to test it but also going to replace it?
clip the leads with some snips. this is to prevent overheating the component by trying to desolder the leads.
38
What is the LM317?
A voltage regulator
39
What does the lm317 do?
it maintains a set voltage output even when the voltage input is changing drastically
40
As it relates to the LM317, what is the dropout voltage?
The dropout voltage is the necessary value difference between the output voltage and input voltage in order for the LM317 to maintain the set voltage effectively.
41
Let’s say you’ve set up a LM317 regulator circuit for 9V output with the input voltage being 12(dropout voltage=3V). What’ll happen to the output voltage if the input and output voltage difference drops below the dropout voltage?
the LM317 will struggle to maintain the voltage the circuit was designed for and start to follow the value of the input voltage.
42
For the LM317, What’s the typical input voltage range where the output voltage will still maintain its set value in a regulator circuit?
Anywhere between 3V above the desired output voltage and 40V.
43
Let’s say you’ve set up a LM317 regulator circuit for 9V output with the input voltage being 12(dropout voltage=3V). What’ll happen to the output voltage if the input voltage goes above up to 30V?
The output voltage will remain at 9V
44
the 3 pin componet you see in the circuit below is an LM317 voltage regulator. What is this circuit below doing?
He’s demonstrating the voltage regulator performance by hooking the LM317 into a voltage divider circiuit.
45
how do you solder a component with short leads onto left over leads that are already soldered into a hole on a circuit board?
put a blob of solder on the circuit board whwre the left over lead is and while heating up the blob, attach the component’s lead to the leftover lead and remove the iron
46
What happens to the voltage output of a transformer if the input voltage exceeds the transformer’s resonant frequency?
The output voltage will start to decrease. The alternating current is changing too fast for the electromagnetic field to keep up strong.
47
Transformer and voice coils have a resonant frequency. As it relates to transformers, what is a resonant frequency?
the natural frequency where a transformer alternates at the highest amplitude. The sweet spot.
48
Why is it bad to supply a transformer with square waves?
The short time frame(less than a second) of the rising edge and falling edge of the change in current will cause extremely high voltage spikes in the transformer. Those voltage spikes can travel from the output windings or reflect backwards from the output windinings through the input windings and damage other components.
49
how do you solder onto through hole leads
make sure iton is touchingboth contact ring and lead. then, steadily push the solder in between the lead and iron tip.
50
whats the difference in shottky and silicon diodes when measuring them in diode mode?
❓silicon diodes are typically .4-.7V in diode mode shottky diodes are typically.15-.3V in diode mode
51
How do you test a potentiometer?
put the ohmeter probes on the leads of the potentiometer and turn the dial/knob. the meter should display a gradual increase or deacrease in resistance within the ohms range of the potentiometer.
52
On some signal generators, how do you increase the output voltage?
By increasing the amplitude dial/knob
53
If you’re trying to see the signal of an active component with an oscilloscope and the displayed signal is very weak, it could be that-
The oscilloscope’s signal amplification knob/dial is turned too low and you need to turn it up so that the oscilloscope essentially zooms in on the received input signal.
54
If you've already turned up the signal amplification on the oscilloscope and the zoomed in signal is all over the place and not a consistent sine wave or signal, you should try-
Tracking to the signal by pressing the button that corresponds to signal tracking and turning the tracking dial/knob.
55
What’s happening in the image below?
The free electrons from the N region have filled in some holes on the P region, which create a net negative charge on the P side. At the same time, since some electrons have left the N region to go to the P region, this creates a net positive charge on the N side. As a result, an area of equilibrium or 0 charge forms at the interface of the P side and N side.
56
What’s a depletion region?
The diffusion process creates a small area of boron anions in the P region and a small area of phosphorus cations in the N region. These ions together generate a stabilized electric field. That stabilized electric field is called the depletion region because there’s a decrease in free charge carriers due to the P-N interaction/junction being at equilibrium.
57
What does bias mean?
A voltage applied to a device, usually a semiconductor device.
58
From an electron’s perspective, what happens when you reverse the direction of current in a P-N junction so that negative voltage is on P side and positive voltage is on N side?
The negative voltage electrons build up in some of the holes at the P region. The buildup of electrons want to move through the N region and make their way to the positive terminal of the power supply but the extra electrons in the N region can’t move and continue the flow of current because they are being repelled by the electrons from the negative voltage that are in the P region. This “going against the grain” restores the P-N junction to its equilibrium state and reforms the depletion region.
59
How do you find the voltage drop of a diode using the diode’s datasheet?
1. Based on the type of diode you're using, assume a voltage drop value within the range of the usual voltage drop values for that type of diode. 2. Calculate the circuit current. 3. Examine the diode datasheet’s voltage drop graph 4. Refer to the calculated current while analyzing the graph 5. Identify your calculated current on the y-axis and find the corresponding voltage drop on the x-axis for the accurate value.
60
This is a signal Generator. What does it do?
It generates AC signals and supplies AC to various components such as transformers or voice coils.
61
This is an oscilloscope. What does it do?
it displays the AC signal of a component that outputs AC signals. Components like transformers or speakers.
62
Why do diodes only allow current in one direction?
a diode combines two semiconductors(P type doping and N type doping) that create a depletion region that shrinks and allows current in one direction but grows and stops current in the other direction.
63
What’s the progression of a diode’s current when the voltage increases?
Non-linear unlike resistors
64
what is this and how do you know?
its a voltage drop graph for a diode. you know because the “1N4148” is the name of a diode. the curve shows the progression of the 1N418’s change in current over change in voltage.
65
Based on the voltage drop graph below, the diode has to be supplied with at least how much voltage in order for it to start conduction and allow any current through it?
About 0.5V.
66
Based on the voltage drop graph below, the diode has to be supplied with at least how much voltage in order for 1A of current to come out of the diode?
About 1V
67
What will happen if you reverse bias a diode with a voltage beyond its maximum voltage rating? too much voltage? Say, supplying a reverse bias of 500V to a diode that can only handle up to 50V of reverse bias voltage.
You will hit the “reverse bias breakdown voltage” property. The diode’s P-N junction will break down and the diode will get burnt up/damaged.
68
What is reverse bias current leakage?
Under normal working conditions, when a diode is supplied reverse bias within its safe ratings, a small amount of current will still leak through in the reverse direction due to thermal excitation. This current is very small but can be concerning when operating in precise digital circuits.
69
What is this diode graph called and what is it showing?
This is a “VI curve” graph. It’s showing what the current will be at a given negative or positive voltage and vice versa. This can be used to show you at what point the diode receives too much reverse voltage, breaks down the P-N junction, and stops inhibiting current flow. Negative values mean reverse bias and positive values mean forward bias.
70
Based on the VI curve graph, around what point does the diode break and allow the full current in the reverse direction?
Around 50V
71
when you see a ceramic cap or polyester film cap that says “104” on it, whats that mean?
A capacitor marked 104 is 10 with 4 more zeros or 100,000pF which is otherwise referred to as a .1 uF capacitor.
72
how do you read polyester film caps with 3 digit numbers on them?
Read three digit numbers as a base capacitance value in picoFarads and a multiplier. The first two digits will indicate the base capacitor value in picoFarads. The third digit will indicate a multiplier to be used on the base number to find the actual value of the capacitor.
73
you see a polyester film cap read 472. what does that mean?
472 would indicate a 4700 pF capacitor. “47”=base picoFerad and “2”=add 2 zeroes.
74
What component does the symbol represent and what is that component primarily used for?
It represents a Zener Diode. They’re used in reverse bias circuits and it maintains a certain voltage. They’re used in voltage regulation.
75
What do these letters and their corresponding percentages represent?
the absolute tolerance value of various components like resistors, capacitors, inductors, etc.
76
What’s the assembly of a Schottky diode? What are its major properties?
Unlike other diodes, Schottky diodes aren’t a combination of a N material and a P material. Schottky diodes are made with one P or N material as a terminal and the other terminal is just a conductive metal. This makes the Schottky diode more conductive and has a low voltage drop due to the absence of a P-N junction that slows down the movement of charges.
77
It takes progressively more energy for light to emit color from Red, to Green, to Blue.
True