Electronics Engineering

Lower noise, higher gain.

A1: The output impedance of a power amplifier is always less than 0.1 ohms. There are no 4 ohm amplifiers on the market!

A2: I actually just bought a new car radio/CD player that specifically shows 4 ohm speakers on the sticker. It is designed to work optimally with 4 ohm speakers. If you use 8 ohm instead, it will work, but you will not get the full power output that is specified. The amp can only kick out so much voltage and so much amperage - if it is designed for 4 ohm speakers, and 200 watts (stereo, so 100 watts per speaker), it can supply 20 volts (P = V^2 / R). If you used 8 ohm speakers to this amplifier, each speaker would only get 50 watts powered at full output voltage.

Alternatively, if it is designed for 8 ohm speakers and 100 watts per speaker, it can provide 40 volts. If you used 4 ohm speakers instead, each speaker could be given 200 watts at 40 volts, resulting in severe overheating and damage to the amplifier.

capacitors can be used for many thing they are one of the most common electrical components they limit current differently at different frequency the higher the frequency the lower resistance. They can also be used to store voltage or build it up to be released all at once in a larger but than could be achieved other wise.

The generation of AC currents and relationship to frequency has to do with the speed of the unit that is turning the generator (prime mover).

The formula for frequency is f = Number of revolutions per minute of the engine (N) x Number of magnetic poles (P) / 120

Speed the prime mover up for a higher frequency, slow the prime mover down for a lower frequency. This is why the generator has to be wound for the voltage that it is going to produce and the frequency that it is to operate on.

This has probably got to do with Iron.

Most transformers consist of large amounts of iron that need time in order to change polarity of a magnetic field.

Faster frequency would make the transformer less efficient. The iron would not manage to become fully magnetized. Slower frequency would make the transformer need more iron, hence becoming heavier. If the size of the iron core were the same and we just lowered the frequency, then as soon as the magnetic field is buildt up, then the rest of the energy until next half wave will be transferred into heat.

It is simply a trade off between efficiency and practicality.

Today's high speed transformers operate at speeds between 20-80 Khz and is only doable due to a special core material of powdered iron that is much easier to magnetize.

Electricity in the early days was DC only. However, some decisions were made to use AC because DC is, at high voltages, very dangerous to humans, something that was demonstrated during the first few 'victims' of the electric chair that in the beginning operated at DC current only.

III LM324 Non-inverting AC Amplifier Circuit

R1 and R2 form a 1/2V+ voltage divider circuit, which biases the op-amp through R3. The circuit input resistance is R3, and the resistance of R4 ranges from several thousand ohms to tens of thousands of ohms.

Strangely there is two directions it is said to flow. The first and wrong is conventional current that is positive to negative. WRONG. Several hundred years ago people guest Electron current is the direction it actually goes in. This is negative to positive.

You'd potentially damage the meter. Whether you do or not is immaterial; if the meter cannot measure the range of voltages you are expecting, it will not give accurate readings over that voltage range, thus you should not use it. Buy a different meter that will measure over that voltage range, or use a voltage divider circuit to get a lower voltage at a certain ratio of what is actually in the circuit (this may be difficult to do, or very simple depending on the circuit tested - the key is you do not want to load the circuit with the voltage divider network).

If all the bulbs are connected in parallel, and there is enough current, yes, the brightness will be the same. The voltage (which is the amount of energy in every charge), remains the same for all bulbs

The formula you are looking for is I = E/R. Amps = Volts/Resistance.

If you say it is normally a 2 Amp circuit, it normally draws 2 amps.

Therefore the original resistance offered to the 12v battery is 2/12 = 6 Ohms.

If you then connect a 12 Ohm resistor in series, they are added, so R = 18 Ohms.

Now if you put 12v across this circuit it will draw 12/18 = 0.66 Amps.

Or

If you just put a 12 Ohm resistor across the 12v supply it will draw 1 Amp.

If the circuit is protected by a 2 Amp fuse, it will not blow, but the resistor will get hot.

Amplitude modulation is one way to carry information on a carrier, such as a

radio signal. Another way is FM (Frequency Modulation). While FM offers greater

clarity for audio, and the higher frequencies that FM use offer a wider

bandwidth, allowing for more information to be transmitted, one application

where FM and digital are not suitable are Aviation communication, which to this

day still use AM analogue. This is because weaker signals can be heard over

stronger, closer ones with AM, allowing for emergency transmissions to have

more chance of being heard over other traffic. Also, AM uses a narrower

bandwidth than FM, allowing more users in a smaller space. This is important for

the lower frequencies of Radio, where space is at a premium (ie shortwave

bands).

The 'sparkling' of diamonds is due to the way the diamonds are cut, plus the fact that diamonds have a high index of refraction results in the total internal reflection of light. The high index of refraction means that diamonds have a very small minimum critical angle (recall the diamond to vacuum in the observation table). The minimum critical angle in a diamond is 24.4 degrees. Therefore, a lot of the incident light experiences total internal reflection inside the diamond. A ray of light can reflect several times in the diamond before exiting through the top of the diamond.

Fibre optics is a technology that uses light to transmit information along a glass table. To achieve the light not escaping as it travels through the cable, it must have a small critical angle so that the light entering it will have an angle of incidence greater than the minimum critical angle for this medium.

error correction

data compression

The simplest application of a UJT is as a relaxation oscillator, which is defined as one in which a capacitor is charged gradually and then discharged rapidly.

In an op-amp, an input on the inverting terminal drives the output in the opposite direction, while an input on the non inverting terminal drives the output in the same direction.

In a normal closed loop negative feedback configuration, there is feedback from output to inverting input, so that the output becomes a known function of input. So long as you stay within limits, the output will go to whatever value is required to make the inputs be the same.

both flip-flop and buffers are used for same purpose(i.e) for holding the data for a specified clock period.....in the case of area reduction these buffers can be used in the place of flip-flop.....

with the help of function generator we found wave in oscilloscope

Connect 50 of them in series. This would have 50 ohm as equivalent. Same way have another 50 pieces in series. This again would have 50 ohm as effective value. Now connect these in parallel to each other. Now the effective would become as 25 ohm.

The whole circuit fails - because the action of the bulb blowing cuts the circuit.

The main difference is specilization. I am a chemical engineer myself, and we have the option of specializing in a wide variety of degrees, such as genetic engineering. Note that chemical engineering is a very broad field dealing with polymers, metallurgy, biology, environmental chemistry, and the list goes on. Genetic engineering, in short, is really a specialization of chemical engineering to specifically biological chemistry.

to made reverse bias junction between gate to source

It means that the loudspeaker maker tells you that his loudspeaker builds an input impedance (load impedance) of Zload = 4 to 8 ohms. In audio we use always voltage matching and so the amplifier output should have a source impedance of smaller Zsource = 0.1 ohm. Scroll down to related links and look for "Damping Factor".

if the aircraft is the standard aluminum airframe. any power ground should be less than 1 Ohm. A digital multimeter is best for the novice. for more serious applications a mega-ohm meter should be used. but be careful, most of this meters output more that 600 Volts.

Switches used in electrical circuits are wired in series with either a parallel or series load. In parallel loads, the switch is upstream from the parallel circuit, so that the switch will shut off all of the parallel circuits.