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Electronics Engineering
Electronics Engineering is a branch of engineering that deals with practical applications of electronic components, devices, systems, or equipment. Electronics are devices that operate on low voltage sources, as in electron tubes, transistors, integrated circuits, and printed circuit boards and use electricity as part of its driving force.
24,372 Questions
What are Disadvantages of digital control?
Unwanted Errors of precision when the analog signal is converted into a quantized, sampled digital signal. The same error arises when the digital signal is then converted into an analog signal for the plant to use.
Why the secondary of the current transformer should not be open circuited?
The secondary of a CT must always have a load connected. An open circuit secondary can result in the development of a dangerously high secondary voltage. If a CT is energized but is not used, the output terminals of the CT must be shorted out.
first you need a analog multimeter. put in your meter in the ohm section x10. then remove the cap in the ckt and discharge that. then connect the multimeter -ve probe to the cap +ve terminal and connect the other terminals.the needle comes to low value then com to infinity, remove the probs then connect multimeters -ve prob to the cap -ve terminal that time look carefully the meter's needle comes to the one value and go back to the infinity that the low value is capacitors equivalent resistance value. the cap is 1000uf the equivalent resistance value is around 15 at x10 .the cap is 100uf the equivalent resistance value is around 15 at x100
It might be helpful to have a working definition of modulation before making a statement as to why it is needed. In fact, with an understanding of what modulation is, it will be obvious why it is included in electronic communications.
Modulation is the "message" or the "intelligence" that is impressed on a radio frequency (RF) carrier. When we transmit a signal, we generate a carrier frequency, and then we modulate it. We "add" the message or the information we wish to transmit by modulating the carrier in some way. There are at least a dozen different modulation schemes ranging from simple to real head scratchers. They either modify the amplitude, the frequency or the phase of the carrier. Let's look at a few.
The simplest modulation technique is taking the transmitted signal and turning it on and off. It is "keyed" to send a series of pulses. Morse code uses on-off keying. In this method of modulation, no modification of the RF carrier signal itself is made. It is simply switched on and off. (It could be looked at as amplitude modulation with the carrier either at zero amplitude or at "maximum" amplitude with nothing in between.) A series of pulses can be transmitted. With Morse code, a short "on" period will send a dot or "dit" out. If we extend the "on" period a bit, we can send a dash or "dah" out. Nothing real sophisticated here, but basic and effective communication. There are obvious limits to how fast information can be transmitted with this modulation scheme. (But don't tell the hams who still use it!)
Most of us are familiar with AM radio. AM is amplitude modulation. The amplitude of the RF carrier is modified to modulate it. The amplitude of the modulating signal will determine the amount that the amplitude of the carrier is changed. (The volume of the modulation determines how much the amplitude of the carrier is changed. The frequency of the modulating signal determines the rate of change of the amplitude of the carrier. (The frequency of the modulation determines how fast the amplitude of the carrier is changed.). The frequency of the carrier is held constant through all this.
How about FM? In frequency modulation, the amplitude of the carrier is constant. It's left alone. But the frequency of the RF carrier is changed. It is swung above and below where it sits (it's assigned center frequency) at a rate proportional to the frequency of the modulating signal, and at an amount proportional to the amplitude of the modulating signal. In FM single sideband, the carrier frequency and the frequencies above the carrier are transmitted and the frequencies below the carrier are suppressed (upper sideband transmission). Or the frequencies below the carrier are transmitted with the carrier and the upper frequencies are suppressed (lower sideband transmission). In conventional television, the video signal is single sideband, suppressed carrier. It's like "regular" upper sideband transmission except the carrier signal is suppressed. Sideband transmission "saves" space on the RF spectrum. And it works because we really don't need "all" of the FM signal to demodulate the signal at the receiver.
Other forms of modulation become more complex. CDMA (code division multiple access), TDMA (time division multiple access) and other methods are used in cell phones to modulate the carrier so the digital data stream can be impressed on the carrier.
Modulation is the addition of intelligence to a carrier signal. It's the message. Modulation is necessary because the point of communication is getting the message through.
A Simple answer:
Simply this... Any communications medium: e.g. Free space - radio waves, Air - Sound waves or radio waves, Optical Fibre - Light, Copper Wires Electrical Anergy (with frequency limits of the copper wire construction) is made for a certain type of signal. But if the signal we want to send is not compatible with the medium, then it does not travel well.
Modulation changes the information we want to send from it's original form, into one that is more compatable with the medium we are trying to use.
For example, your computer speaks digital over a TCP/IP LAN which requires CAT 5 or better rated cables,, but to connect to your internet service provider (ISP), you need to send the signal over the wires of the telephone company (made for voice tones). To make this connection, and ADSL modem (modulator/demodulator) is used to convert the data into audio tones, which pass over the telephone line, and at the far end are converted back to digital to join the service providers network. in the reverse direct the ISP does the same, and the signals are de-modulated, back to data for your network.
Or in simple terms, Its about best use of the medium. Everything else is just a away of doing it. And there are a lot of possible ways to choose.
What is PLC programming and who uses it?
PLC stands for "programmable logic controller". PLC's are usually used to control machinery in automated processes such as manufacturing. PLC programmers usually complete a trade school certificate before starting their careers.
Advantages and disadvantages of time division multiplexing?
Advantages of TDMA
1. The user gets full bandwidth of the channel in a particuler time slot.
2. For bursty signals such as voice or speech TDMA gives maximum utilization of the channel
3. most suitable technique for digital transmission.
Disadvantages of TDMA
1. it is not much suitable for continues signals
2. extra guard time are necessary
3. synchronization is necessary.
Can you power a motor directly form a dynamo?
Yes, like the dynamo on a bicycle that provides power for the light, instead it can run an electric motor with the help of a few cheap diodes(Bridge diode setup)
What is the effect of bandwidth on a digital signals?
Bandwidth is an inherent characteristic of a given transmission channel, or is determined by the narrowest-bandwidth component of the system. The bandwidth of a channel will limit the possible attainable data rates. This is shown simply by Shannon's Theorem, which states
C = B log_2 (1+P_signal/P_noise),
where C is the channel capacity in bps, B is the channel bandwidth in Hz, P_signal is the power of the detected signal in W, and P_noise is the noise power of the detected signal in W.
As an example, consider a standard phone line (i.e., using a dial-up modem). Standard phone lines have a bandwidth of about 3.4 kHz and a signal-to-noise ratio of about 10,000. Using this information, we get
C = (3.4 kHz) log_2 (1+10,000) = 45 kbps.
Dial-up modems can actually get as high as 56 kbps, but that is beyond the scope of this question. In general Shannon's Theorem can provide a fairly accurate way to predict the possible data rates for a given transmission channel if the bandwidth and resulting signal and noise powers are known.
What is the function of an emitter?
emitter collects output current produced in resister
Wrong. An emitter in a semiconductor emits majority current carriers (electrons or holes) into the junction between it and the base..
Scroll down to related links and look at "Ohm's law - calculator and formulas".
How must the two transistor junctions be biased for proper transistor amplifier operations?
A: Actually it is only one transistor required for amplification the other junction can be a diode. As current Begin to flow it causes a bias across one junction which is opposite biasing for the other, A good differential amplifier will have those junction virtually at the same point with a very good current source because any mismatched will cause and output without any input. It is called voltage offset on the other end if the feedback current is very small it will also produce an output voltage offset known as current offset or basically errors
How do you wire in a voltmeter?
A voltmeter needs to be connected in parallel with the part of the circuit you are checking. It records a change in voltage, and has a high internal resistance, so it cannot be connected in series unless you want to screw up the circuit. Set the meter to AC or DC volts and place the wires of the terminal across the resistor, switch, or any other potentially resistive part of the circuit.
Why charges exit a circuit with less energy they had when they entered the circut?
resistance in the circuit
How air condition system is closed loop control system?
Air conditioner system senses the room temperature and then decides how much cooling has to be provided to room as per the setting. Say u need only 20 degree Celsius only.
To elaborate, in a closed loop system, the output in some way shape or form is fed back into the input of the control system. With an air conditioning system, the output is temperature. This temperature is read, and fed back into the control system to determine if additional cooling is needed or not.
An example of an open loop system would be if you programmed the air conditioning to turn on from 11AM to 5PM, then turn off. The output of the system (temperature) doesn't effect the input (when the system runs).
Why dc motor is not named as conduction motor?
In dc motors, the electric power is conducted directly to the armature (i.e., rotating part) through brushes & commutator. Hence, in this sense a dc motor can be called as a Conduction motor.
However, in ac motors, the rotor does not receive any electric power by conduction but by induction in exactly the same way as the secondary of a two winding transformer receives its power from the primary. That is why such motors are called as Induction motors. An induction motor can be treated as a rotating transformer i.e., one in which primary winding is stationary but secondary is free to rotate.
What is the advantages of variable resistor?
When we want to regulate somthing ;we use variable resistors for example :volume control in radios and volume in headset. Also , the variable resistors can forms a potential devider in which the overall resistance between the two end points remain the same,but the ratio of the two resistors in the legs changes.so the variable resistor is affectively a potential divider.
Also, the variable resistor can forms a potential divider in which the overall resistance between the two end points remains the same, but the ratio of the two resistors in the legs changes. So, the variable resistor is effectively a potential divider.
The Rectifier is an electronic device, which converts an AC waveform(Usually a Bi-directional waveform with Zero Average value) to a Pulsating DC waveform (Uni-directional waveform with Nonzero Average value). As AC wave (Sinusoidal) has two half cycles, namely - Positive Half cycle & Negative Half cycle If a Rectifier does it's operation only in one half of the cycles, it is known as Half Wave Rectifier. Similarly, If a Rectifier does it's operation in both the half cycles, it is known as Full Wave Rectifier.
What color band markings would be used on a 2.2 k resistor?
A 2.2 k resistor would be banded red, red, red, and possibly other bands depending on tolerance, etc.
The first two bands, red and red, mean 2 and 2. The third band means 2 zeros. The result is 2200.
0 black
1 brown
2 red
3 orange
4 yellow
5 green
6 blue
7 violet
8 grey
9 white
Fourth band:
none 20%
silver 10%
gold 5%
If the third band is gold or silver, then the multiplier is 0.1 or 0.01, respectively. For example, red, red, silver means 0.22 ohms.
What happens to the current in a circuit if one resistance is doubled or halved?
P1 = V I1, Therefore, if P2=0.5*P1, then
I2=0.5*P1/V, or 0.5*I1
and if P3=2*P1, then
I3=2*P1/V, or 2*I1
In other words, current is proportional to power and inversely proportional to voltage.
-48 v is given to BTS because in this voltage Noise
generation is minimum.
Because two terminal comes out from the battery and
through red color wire we ground the +ive terminal so that
possibility of noise interference will get zero because noise
occurs only in the +ive terminal that's why we use -ive
voltage in the BTS.
What does the variable resistor do in a circuit?
It is used to vary the voltage/current flow in a circuit.
