1. According to Figure 3? 10? 4 when connecting the circuit to do experiments, sometimes the pointer of galvanometer G always points to zero or never points to zero, so adjust the A and B terminals anyway. What are the possible reasons for the two situations?
Answer: It always refers to zero because the measuring circuit is open. The reason why it never points to zero: (1)E and Ex are not in the right polarity; (2) the working circuit is open; (3) The total voltage drop across 3)RAB is less than the smaller value of ES and Ex.
2. A potentiometer can be used to measure the internal resistance of the battery, and its circuit is shown in Figure 3? 10? As shown in Figure 6, assuming that the working battery E > EX, the Rc is unchanged after adjustment during the test, and Rx is a high-precision resistance box. R is a uniform resistance wire. L 1 and L2 are the length of the resistance wire when the potentiometer is in compensation state when Kx is off and on, respectively. It is proved that the internal resistance of battery Ex is r=[(L 1-L2)/L2]Rx(Rx is known).
Answer: Proof: Let A be the potential difference of unit length on R and Vx be the terminal voltage of K2.
Then it is: ex = al 1-( 1)
Vx=AL2 - (2)
And VX = ex-IR = ex-{ex/(r+rx)} r = rx/(r+rx) ex.
Substitute into formula (2):
{Rx/(r+Rx)}Ex=AL2 - (3)
(1) divided by (3):
r={(L 1-L2)/L2}Rx
3. Box potentiometer can be used to measure resistance or calibrate ammeter. Figure 3? 10? 7( 1), ammeter A to be calibrated and resistance Rx to be measured. R0 is a high-precision adjustable resistance box, and its value can be read directly. (2) It is UJ37 box potentiometer. How can I calculate Rx? How to correct table a
Answer: (1) Measure the resistance Rx.
① Adjust the resistance of the variable precision resistor box R0 (used as a standard resistor) to make the ammeter deflect properly, and if possible, make R0 close to Rx.
② Connect 3 points to Ex(+) and 2 points to Ex(-), and measure VX (potential difference between two ends of Rx).
③ Connect 4 points to Ex(+) and 3 points to Ex(-), keep the current constant, and measure v0 (potential difference between the two ends of R0).
④ Because Rx and R0 pass the same current, Rx=(Vx/V0)R0.
(2) Standard ammeter
① Connect Ex(+) at 4 o'clock and Ex(-) at 3 o'clock, and adjust R0 so that ammeter A indicates the first calibration point. Measure the potential difference across R0 (V 1) and get the current at the first calibration point (I 1 = V 1/R0).
② Measure the currents I2, I3, ... at the same calibration point in the same way.
③ Make calibration curve.
4. as shown in figure 3? 10? The potentiometer shown in fig. 4, where A~B are resistance wires with the length of 1 1m, if a=0. 1V/m), the voltage of 1 1m drops to1. In order to reduce the error, Figure 3? 10? 8 shows the circuit. Figure 3? 10? 8. The resistance wire AB with the length of 1 1m is connected in series with two larger resistors R 1 and R2. If the total resistance of A B is known as R, then the total voltage on R 1, R2 and R is 1. 1V, and A = 0.1m on the design AB (1m) resistance wire. How about R 1+? If the electromotive force of standard battery E0 is 1.0 186 V, what are the maximum and minimum values of R 1 (expressed by line resistance r)?
Answer: (1) When the potential difference of resistance wire per unit length of potentiometer is V0, the potential difference on resistance wire AB is VAB= 1 1V0. When the unit potential difference is V0', the potential difference on AB is VAB'= 1 1V0'. At this time, the working currents I' = VAB'/R. and VAB = I'(r 1+R2)+VAB',
R 1+R2 =(VAB-VAB ')/I ' =[(VAB/VAB ')- 1]R =[(v 0/v 0 ')- 1]R = 999 R。
(2) If R2i'= E0, R 1 is the minimum value.
There is r1I'+E0+I 'r =1.1.
r 1min =( 1. 1-E0-I′r)/I = 73r
If R2i ′+IR ′ = E0, R 1 max.
There is r1I'+E0 =1.1.
r 1 max =( 1. 1-E0)/I′= 74r
Design experiment 7 Calibrating ammeter with potentiometer
First, the experimental purpose
1, understand the working principle of potentiometer and master the use of potentiometer;
2. Calibrate the microammeter with UJ36 potentiometer.
Second, the design requirements
1. Design the circuit for calibrating microammeter with potentiometer, and draw the circuit diagram.
2. Select appropriate instruments and parameters among the following instruments, and calibrate the 100μA, 1.5 microammeter with UJ36 potentiometer:
①DZX2l resistor box ② sliding rheostat ③ regulated power supply ④ galvanometer ⑤ voltmeter ⑤ switch ⑦ conductor.
3. Calibrate the microammeter with the selected instrument and make the calibration curve.
Third, think about the problem
1, potentiometer is used to measure electromotive force or voltage, how to use it to measure the current through ammeter?
2. When verifying the ammeter, how to make the current flowing through the ammeter change as required within the whole range of the ammeter?
3. How to do the ammeter calibration curve? How to calculate the correction value? How to get the correct current value from the indicated value of the electric meter according to the calibration curve?
4. Can you design a circuit to calibrate a voltmeter with a range of 3V with a potentiometer?
The largest scientific instrument
The largest scientific instrument is the large positron storage ring (LEP), which is located in Sien, with a circumference of 27 kilometers.
The diameter of the ring itself is 3.8 meters. Scientific instruments weighing more than 60,000 tons are placed in pipelines and 8 working areas.
The newest and heaviest element.
199 1 year 1 month, Lawrence Livermore National Laboratory, California, USA and Dubna Joint Nuclear Research Institute, Russia.
Scientists claim to have discovered the latest and heaviest element in the world, jujube element 1 14. It is said that the element contains 1 14 protons.
More stable than other super-heavy atoms. This element is produced by the bombardment of neutron-rich plutonium homologues by calcium isotopes.
The strongest acidic solution
The Ph value of strong acid and strong alkali solution tends to 0 and 14 respectively, but it is far from enough to describe it as "strong acid".
. The strongest of the strong acids is hydrofluoric acid containing 80% soluble antimony fluoride. The acidity of this acidic solution has not yet been determined, but even if
The slightly weak solution with 50% solubility is also more acidic than concentrated sulfuric acid solution 10 18 times.
The deadliest synthetic chemical.
Among the 75 known dioxins, 2,3,7,8-tetrachlorodibenzo is the most deadly to dioxins, which is more deadly than cyanide.
Toxicity 15000 times.
The most magnetic substance
The maximum energy output of Nd2Fe 14B NdFe65438 is 280 kJ/m3 (the so-called energy output is in specific operation).
Point, the maximum energy that a magnet can provide).
The most powerful nerve gas
1952, a super toxic gas was developed at the British chemical defense experimental base in Burton, Wiltshire. The toxicity of this substance
Sex is 300 times that of phosgene gas used in World War I.. The air density of this substance reaches 10 mg/m3, which can be fatal.
The minimum lethal dose for oral administration is 0.3 mg.
The most bitter substance
The basic component of the most bitter substance is cation, which is made into benzoate and saccharified after commercial development.
Its taste detection standard can be as low as1/500 million. 11100 million diluted solution can still leave a long bitter taste.
The sweetest substance
There is an extract of plant aril (the so-called extract is an appendage on some plant seeds), which is as sweet as sugar cane.
The sweetness of sugar is 6 150 times. This plant can be found in parts of West Africa.
The densest element
The densest substance on the earth is osmium, with a value of 22.8 g/cm3. According to calculations, a single component of the black hole core
The density of is infinite.
The least dense substance
The lowest density of solid matter is silica gel. Silicon combines together to form tiny spheres, which combine with oxygen atoms.
Long strings, separated by airbags. The lightest aerogel has a density of only 0.005g/m3, which is produced in the United States.
Lawrence Livermore National Laboratory, California, USA. This material will be mainly used to collect micrometeoroids and comets in space.
Fragments left on the tail.
maximum temperature
The highest temperature that humans can produce is 5 1 100 million degrees Celsius, which is about 30 times higher than the temperature in the center of the sun. This is the temperature in New Jersey, USA.
The plasma mixture of deuterium and tritium was used in the tokamak nuclear fusion reactor of Princeton plasma physics laboratory in May 1994.
Created on the 27th.
Maximum superconducting temperature
1April, 993, in the laboratory of Zurich, Switzerland, the mixture of oxides of mercury, barium, calcium and copper HGB _ 2ac23cu3o 1+
X and hgba 2 cacu 2 o 6+x have good superconductivity, and the highest transfer temperature is-140.7 C. The higher temperatures are as follows
Not confirmed.
The most absorbent substance
In August 1974, the US Department of Agricultural Research and Service announced that a super absorbent can be absorbed into water after iron treatment.
Collect 130 times its own weight. Starch extract accounts for 50%, acrylamide and acrylic acid account for 25% respectively. This substance has existed for a long time.
The ability to maintain temperature balance makes it an ideal raw material for reusing ice packs, which is in Detroit, Michigan, USA.
In a game, it can be confirmed that the substance lowers the body temperature for 14 year old baseball.
The hottest flame
Basic carbon nitride can produce the hottest flame, and at 1 atmospheric pressure, it can produce a fire with a temperature as high as 4988℃.
Flame.
minimum air temperature
The absolute zero temperature-that is, zero on the absolute temperature scale-is equivalent to -273. 15℃. When it reaches this temperature, all the atoms split.
The motion of that sub-heater will stop. The lowest temperature reached is 280 degrees Fahrenheit, which is 1993 in Finland in February.
The Scientific Cryogenic Laboratory has produced and published the nuclear demagnetization device it uses.
The most elusive protein.
Biochemists from Harvard Medical College in Boston, Massachusetts studied protein's behavior in 1990.
Have made a major discovery. For a long time, people thought that the protein population composed of amino acids could only be composed of other species called keratin.
Protein broke down and reorganized. Scientists at Harvard University monitor a tiny protein called pheromone.
Cut from a long protein chain and reconnect the cuts at both ends of the protein chain to eliminate any protein.
The sign on the chain. It is expected that the unique nature of protein will be able to fight diseases such as tuberculosis and leprosy.
Give us a hand.
The largest galaxy
The central galaxy of Abel 2029 cluster is about 65.438+0.7 billion light years away from the Earth, with a diameter of 56,000 light years-equivalent to silver.
80 times the diameter of the water system.
The brightest galaxy
The brightest galaxy is AMP08279+5255, a distant galaxy with a red shift of 3.87, which is very bright.
The degree is 5× 10 15 times the brightness of the sun.
Farthest object
The farthest known celestial body is an unknown galaxy with a redshift of 6.68, that is, Little Chen Wen, Kenneth, Lanzetta and Sebastian.
Ann Pascarella (both Americans) found it at 1998. What we see is that the age of the Milky Way is only 10 now.
The scene of the universe at 30%, which is the farthest prehistoric scene we have got so far.
The largest star
Orion, an M-class Supergiant star, has a diameter of 980 million kilometers, 700 times larger than the sun.
The largest satellite
The largest satellite in the planets of the solar system is Ganymede in Jupiter's orbit, with a diameter of 5268km and a mass of 1.4828.
0 tons, 2.0 17 times the mass of the moon.
The most hidden star
1February, 999, Dr. Robinson Mohaib of the University of Maryland announced the discovery of a huge halo star at the edge of the Milky Way.
An organization called MACHOS. Although we can't see this star, it's because its gravity refracts starlight from other backgrounds.
As scientists know, this group of stars may have reflective satellites revolving around them and there is life. Life can see its own reflection.
We know nothing about our galaxy, just as we know nothing about theirs.
Minimal amount of substance
1997 produced a chemical called seaborg (Sg- 106 element), the number of which is only 7 atoms. about
Therefore, it was named in memory of Dr Glenn Seeburg, the late Nobel Prize winner in physics and the discoverer of plutonium.
The smallest product
The terminal of scanning tunneling microscope probe is a single atom, which constitutes the last three layers of the world's smallest artificial pyramid: seven layers.
Atoms, 3 atoms and 1 atom. 1990 65438+ 10, scientist, IBM Amorden Research Center, San Jose, California, USA.
It is said that they used scanning tunneling microscope to move and rearrange individual atoms on xenon and nickel surfaces in order to write the company's initials.
Mother: IBM. Horses in other laboratories have applied this technique to individual atoms of other elements.
The most heat-insulating substance
1in April 1993, Maurice Ward developed a composite material and announced its existence. This substance is called NFAAR, which can be abbreviated as NFAAR.
Temperature of phase isolator (10000 degrees).
The strongest light source
Among the light sources that continuously emit light, 198 is the strongest.
In March 2004, high-pressure argon arc lamps with 365,438+0.3 kW and 654,380+200,000 candelas were completed.
The strongest current
Scientists at Oak Ridge National Laboratory in the United States obtained the strongest current so far in April 1996. They're in the superconducting wire.
A current of 2 million amperes flows through the wire. The maximum current that a household wire can carry is 1000 amp.
The largest sun station
In terms of power generation capacity, the world's largest solar power generation facility is located in Mojave Desert, California, USA.
Hubble Lake Solar Station operated by the University of California Operations Service Center. The power generation capacity of this solar power station is 160 MW. The cover of the power station
Covers an area of 5 18 hectares.
Maximum DC engine
The largest DC generator is designed by mitsubishi electric company, with a total power generation capacity of 5 1300 kW, which provides energy for nuclear fusion. this
The generator seat is 16.5 meters long and weighs 353 tons. It was installed in Japan Atomic Energy Research Institute in May 1995.
The fastest centrifuge
1975, the University of Birmingham, England, rotated a tapered carbon fiber rod with a length of 15.2 cm in a vacuum state, creating.
The maximum speed of manual rotation is 7250 km/h1923, and Swiss chemist Theodore Swardberg invented ultracentrifugation.
A machine for separating organic compounds. In order to make it faster, scientists installed a magnetic field under vacuum to help it rotate.
A device for reducing frictional resistance.
The most sophisticated balance
The 4 108 ultramicrobalance produced in Germany can measure the lightest objects, with the highest accuracy of 0.5 μ g and the accuracy of 0.0 1 μ g, or
1× 10-8g, which is equivalent to 1/60 of the ink used on this page for a period of time.
The finest cutting tool
According to June 1983, the large-scale optical diamond cutting in Lawrence Livermore National Laboratory, California, USA.
This machine can cut a hair vertically 3000 times.
The fastest signal
1996, a group of scientists at the University of Cologne in Germany claimed that they had completed Einstein's special theory of relativity.
The speed signals. This signal is part of Mozart's 40th symphony, which is used to confirm the findings of previous experiments.
In this experiment, microwave is divided into two parts to confirm the findings of the previous experiment. In this experiment, microwave is divided into two parts.
One part is conducted through a special filtering device, and the other part is conducted through air. Both parts should travel at the speed of light.
But the speed of the signal passing through the conversion device is 4.7 times faster than that passing through the air.
The longest solar eclipse
The longest duration of an eclipse (the moon is between the sun and the earth) is 7 minutes 3 1 second. 1955 occurred in western Philadelphia and continued.
This eclipse lasted 7 minutes and 8 seconds, the longest in recent years. It is predicted that there will be a duration in the mid-Atlantic in 2 186.
This is a solar eclipse of 7 minutes and 29 seconds. 1995, a mother and son were photographed during the solar eclipse in Bangkok, Thailand.
A total solar eclipse occurred in some parts of this country. The longest duration of an eclipse (the shadow of the moon on the earth) is 1 hour and 47 minutes. 200
In July16,0, people will see this scene on the west coast of North America.
The longest scientific index
1992+version 2 of Chemical Abstracts completed in February has a total index of 2 15880 pages, which is divided into 1 15 volumes, with entry 3.
5 137626, weighing 246.7 kg. This book provides an index reference for 3,052,700 published articles in the field of chemistry.
The most complete genome sequence of multicellular animals
The first multicellular animal with complete gene sequencing was an earthworm with a body length of 1mm, which lived in soil. although
An adult's whole body only includes 959 cells (the number of human cells is hundreds of millions), but this insect contains 65438+ billion gene bases, which are composed of * * * *.
There are 18000 genes, and more than 50% of the known human cells are similar to the morphology of this insect. The genome depicting the worm is Sidney.
Dr brenner's mental work, he started this project in the laboratory of the British Molecular Biomedical Research Council in the 1960s.
Research and accurate ranking were conducted in 1990.
The earliest machine that made living things float in the air.
1997, Dr. Andrew Kyoto Electronics Industry Co., Ltd. of Nijmegen University in Amsterdam, the Netherlands and his colleagues made a superconducting magnet.
A live frog floats in midair. They also did similar experiments with fish and crickets.
The earliest long-distance transmission
Researchers led by Professor Anton Salinger of Beullac University in Austria have taken a photon far away.
Teleportation. If there is no relationship between the two, the physical properties of a photon will immediately transfer to another photon.
The experiment needs three photons, one original photon and two entangled photons. The physical properties of these two photons (or
Spin) complementary. When the rotation of the original photon and another photon is measured, another photon replaces the first photon.
Do a spin. 19 The popular sci-fi TV series "Star Trek" in the 1960s first aroused people's awareness of long-distance love.
General interest in transmission.
References:
Light of science and technology