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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
Resistance:
Electrical resistance describes how an electrical conductor (a wire) opposes the flow of an electrical current (flow of electrons). To overcome this opposition a voltage (a energy) must dropped (used) across the conductor (wire). Resistance can be described by ohms law:
Ohms Law: R = V / I (Resistance = Voltage / Current) (resistance measured in ohms)
where:
Voltage [V]= the energy lost across an component (voltage measured in volts).
Current [I] = the charge (electrons) flowing through an component (current measured in Amps).
Electrical resistance can be thought of as sticking your hand out a car window. The faster [current] you drive the harder the wind presses [resistance] against you hand and therefore it takes more energy [voltage] to hold your hand steady.
When trying to overcome electrical resistance, the electrical energy lost is turned into heat. This is how the elements of a household stove, toaster, and fan heater work. Because of the vacuum in a light bulb, the electrical energy lost is instead turned into light. It can be seen the electrical resistance plays a large role in modern life.
Resistor:
The resistor is the most common electronic component and is used to limit and/or control the voltage and current in an electronic circuit. Resistors are carefully manufactured to provide a predetermined value of electrical resistance which may range from 0.1 ohms to 100,000,000 ohms, depending on the application. The physical size of a resistor also varies dependant on the amount of power passing through the resistor, given by:
P = V x I (Power = Voltage x Current) (power measured in watts)
There are also many types of resistors including:
· Variable Resistor - changes resistance when its shaft is rotated (volume knob on a stereo).
· Thermistor - changes resistance when the temperature changes (used in a thermostat).
· Light Dependant Resistor (LDR) - changes resistance when the lighting changes (used in children's night-lights).
Resistor Example:
An LED is a small red light (such as the one on the front of most TVs) and requires 2.0 volts and 0.02 amps to operate correctly. If we connected that LED up directly to a 12 volt battery, the voltage would be too high, and too much current would flow... the LED would blow up. We need to use a resistor to limit the voltage and current.
But which value of resistance should the have resistor? Uses ohms law:
R = V / I = (12.0 - 2.0) / 0.02 = 500 ohms
(Note: the voltage across the resistor is the battery voltage minus the voltage we want across the LED)
But which value of power should the resistor be capable of handling?
P = V x I = (12.0 - 2.0) / 0.02 = 0.2 Watts
ANSWER: HOW ELSE WE BE ABLE TO AMPLIFY A SIGNAL that is the answer.
What is difference between pulse width modulation and pulse position modulation?
Frequency modulation, as the name suggests, modulates the carrier by changing the frequency of the signal emitted.
Pulse width modulation, changes the on-time of a square wave, but leaves the frequency of the carrier wave unchanged.
So, in frequency modulation, the frequency will vary between, say, 80kHz and 120kHz with a constant power level, but in pulse width modulation, the frequency will stay at 100kHz, but the on-time (the length of each pulse) will vary, hence the power level will vary accordingly.
What are active and passive transducers?
An example of a passive transducer is differential transformers. The reason why is because passive transducers require an external power supply to operate.
What Is significance of schottky transistor in TTL gates?
A diode in general lets current flow more in one direction than the other. This can be used in many configurations in an electronic circuit, with one of the more common uses in memory and decision making circuits. With more of our electronic devices running on batteries, manufacturing processes are finally realizing that people will probably buy the device that has a longer battery life over other considerations. Wikipedia contributors contend that the metal-semiconductor junction switches faster and operates at lower voltage.
What is the current in a 10V circuit if the resistance is 2Ω?
If a resistor has a current of 2 amperes when connected to a single battery, connecting a second identical battery in parallel with the first will not change the current through the resistor.
This is because the voltage across the resistor will not change. Yes, the current capacity of the battery (pair) will double, but the voltage will not change.
The exception is if the battery does not have the capacity to supply 2 amperes without sagging in output voltage. In this case, adding the second battery will slightly increase the current through the resistor.
(By the way, without some kind of equalizing circuit, it is not a good idea to connect batteries in parallel. This is because slight differences in voltage could create substantial current flows through the batteries, and possibly damage, fire, and/or explosion.)
Voltage is a build up of electrons at one location relative to another location. To form a voltage gradient (difference), you need to somehow build up electrons at one location, or remove electrons from one location. Shuffling your feet on a thick carpet can do this!
Is there such a thing as 115V 3 phase?
No!
The concept of three phase alternating electricity refers to the relational phase differential of three alternating current single phase sine waves, each displaced 120 degrees of phase angle from the other.
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Addetion:
still the is a three wire DC transmission system.
usually DC transmission used for several resone but the most know one is when the transmission line is longer than 600 km
Are the voltage and current in phase in a circuit of pure resistance?
Assuming that by the question you mean a circuit with a resistance, but no inductance, or capacitance, then yes, the voltage and current will remain in phase.
Reasoning:
The formula V = IR or... Voltage is equal to Current multiplied by Resistance, is (should be!) well known by school students, however this formula assumes that voltage and current are each constants.
This formula can be extended to apply to voltages and currents that vary with time, as in the following equation:
V(t) = I(t) R
Since R will be a constant resistance expressed in Ohms (or more formally, an impedance that contains no imaginary part: a real number), there is nothing in the formula that could introduce a phase shift.
(See the related link below for a wikipedia article on impedance.)
Why 11.0592mhz crystal is used with 8051?
In some systems the CPU and bus timing is a limit to the highest and sometimes the lowest CPU clock frequency, so the clock needs to be stable enough to guarantee timing requirements are met according to the design and the specification.
Can you explain how a voltmeter and ammeter work?
In parallel with the element you wish to measure the voltage across.
Which of what following? The inductance of the coil must be higher than the resistance of the coil, since the supply is providing 200*10 = 2000VA.
2000VA =sqrt[ (I^2 * R)^2 + (I^2 * L)^2]
4000000VA = I^4*R^2 + I^4*L^2
400 = R^2 + L^2
and 1000Watts = R*I^2, so R = 10 ohms
400 = 100 + L^2
L = 17.3 ohms
Assembler directives in microprocessor?
Manual coding of 8086 is difficult hence we use a assembler or a compiler. Note that the microprocessor should be able to interpret your discussions via the program. Suppose if the instruction corresponds to word(16 bits), we use assembler directive WORD PTR, but when assembler is contacting the processor it sets a bit called 'w' indicating its a byte operation.
What is meant by sampling in analog to digital conversion?
while conversion of analog signal to digital signal, we need to convert continuous analog signal to discrete signal. this can be done by dividing the analog signal into specific time slots. this process is known as sampling. there is a condition for sampling that can be given as follows.
fs<=2fm
Light Emitting Diode (LED) & the Avalanche Diode. These are two types of diodes ,but there are more
What is the wave length of a 100MHz FM radio?
What is the wave length of 100 Hz? Answer You mean a sound wave in air. At a temperature of 20 degrees Celsius or 68 degrees Fahrenheit there is the speed of sound c = 343 meters per second. For a tone of f = 100 Hz the wavelength is lambda = c / f = 343 / 100 = 3.43 meters.
The equation for the relationship between wavelength and frequency is X = frequency * wavelength, where X = the speed of the particle. For light, the wavelength of 100 Hz is 2.99 E8 cm, and for sound, the wavelength is 60 m.
How do you connect diodes in series?
Connect positive to negative, leaving the end positive and negative connections free to power circuits or devices. Connecting batteries in series adds the voltage of the batteries. For instance, connecting three 12v car batteries in series will create a total of 36v, enough for welding.
What is induction and inductive reactance?
resistance is real, the other purely imaginary.
AnswerResistance is the opposition to the flow of current (AC or DC) which is proportional to a conductor's cross-sectional area and resistivity, and inversely proportional to its length. Reactance is the opposition to AC current due to either the circuit's inductance or its capacitance, and are termed inductive reactance and capacitive reactance. Resistance and reactance are both measured in ohms.
Inductive reactance is proportional to the circuit's inductance and the frequency of the supply; capacitive reactance is inversely proportional to the circuit's capacitance and the frequency of its supply. In other words, inductive reactance increases with frequency, whereas capacitive reactance decreases with frequency.
All AC circuits contain resistance, and most contain some degree of inductance and/or capacitance. So the opposition offered by a circuit to AC current includes resistance together with some combination of inductive and/or capacitive reactance.
It's incorrect to suggest that reactance is 'imaginary'in the every day sense of the word -it exists, so it must be 'real'. In this context, 'imaginary' is a mathematical term that indicates that if resistance and reactance were represented in a vector diagram (called an 'impedence diagram'), then reactance quantity would lie at right-angles to the resistance quantity. For this reason, the overall opposition to current flow, which is called impedance, is not the algebraic sum of resistance and reactance, but the vector sum of the two. So, for example, if a circuit had a resistance of, say, 4 ohms, and its inductive reactance was 3 ohms, then its impedance would be 5 ohms -not 7 ohms.
Although we can represent resistance and reactance using a vector diagram (impedance diagram), strictly-speaking the quantities themselves are not vector quantities. The impedance diagram is created as a result of a phasor (vector) diagram representing the current and voltage relationships in the AC circuit.
What does 60hz alternating current do?
Direct current (DC) electrical power from a battery has no phase reversal of the electron flow in the electrical circuit. Electrons always flow from the negative terminal to the positive terminal of the battery in the wires of the circuit.
In alternating current (AC), there is a periodic reversal of the flow of electrons (e.g. current) through the wires of the circuit. 60 Hertz refers to the frequency of that reversal of flow. 60 Hz is equal to 60 cycles per second. So AC current from your wall socket in the United States is reversing directions 60 times each second. The cycling is caused by design of the generators used in the power plants that produce the electricity. The current (polarity) reverses direction 120 times each second. Twice in each cycle on a 60 Hz system. Once to the positive and then once to the negative in one cycle.
When current flows through a wire what are they called?
Current flow is when charge moves from one point to another. It is measured in coulombs per second, which is more commonly known as amperes.
What is OR gate in logic gate?
1. NAND gate is used to invert the input A (by connecting A to both inputs).
2. NAND gate used to invert B the same way
3. Now put A' and B' into into a third NAND gate. The output will be (A'B')' which is equivalent to A+B.
What a device that protects an electric circuit from too much current?
Circuit Breakers and Fuses limit the amount of current flowing through the circuit.
