Option I
1. Who discovered the phenomenon of electromagnetic induction?
a) X. Oersted; b) Sh. Coulomb;
c) A. Volta; d) A. Ampère;
e) M. Faraday; f) D. Maxwell.
2. Coil leads of copper wire are connected to a sensitive
EMF of electromagnetic induction in the coil?
a permanent magnet is inserted into the coil;
a permanent magnet is removed from the coil;
the permanent magnet rotates around its longitudinal axis inside the coil.
a) only in case 1; b) only in case 2;
c) only in case 3; d) in cases 1 and 2;
e) in cases 1, 2 and 3.
3. What is the name of the physical quantity equal to the product of the moduleIN
magnetic field induction per areaSsurface penetrated by the magnetic
filament field, and the cosine of the angleα
between vectorINinduction and normal
nto this surface?
a) inductance; b) magnetic flux;
c) magnetic induction; d) self-induction;
e) magnetic field energy.
4. What is the name of the unit of measurement of magnetic flux?
a) Tesla; b) weber;
5. At points 1. 2. 3 the location of the magnetic arrows is shown (Fig. 68) Draw how the magnetic induction vector d) henry is directed at these points. Points 1, 2, 3 show the location of the magnetic needles (Fig. 68). Draw how the magnetic induction vector is directed at these points.
6Lines of magnetic field inductions go from left to right parallel to the plane of the sheet, the conductor with current is perpendicular to the plane of the sheet, and the current is directed to the plane of the notebook. The vector of the Ampere force acting on the conductor is directed ...
a) to the right; b) to the left;
c) up; d) down.
Option II
1. What is the name of the phenomenon of the occurrence of an electric current in a closed
that circuit when changing the magnetic flux through the circuit?
a) electrostatic induction; b) the phenomenon of magnetization;
c) Ampere force; d) Lorentz force;
e) electrolysis; f) electromagnetic induction.
2.
The conclusions of the coil of copper wire are attached to the sensitive
galvanometer. In which of the following experiments will the galvanometer detect
the occurrence of EMF of electromagnetic induction in the coil?
a permanent magnet is inserted into the coil;
the coil is put on a magnet;
the coil revolves around a magnet inside it.
a) in cases 1, 2 and 3; b) in cases 1 and 2;
c) only in case 1; d) only in case 2;
e) only in case 3.
3. Which of the following expressions determines the magnetic flux?
a) BS cosα b) ∆F/∆t
B) qVBsinα; d) qVBI;
e) IBl sin α .
4. The unit of change of what physical quantity is 1 weber?
a) magnetic field induction; b) electrical capacity;
c) self-induction; d) magnetic flux;
e) inductance.
5. Draw a picture of the lines of magnetic induction at
the flow of current through the coil (Fig. 69), wound on
cardboard cylinder. How will this picture change when:
a) increasing the current in the coil?
b) a decrease in the number of turns wound on a coil?
c) into the introduction of an iron core into it?
6. Conductor with current lies in the plane of the sheet. A current flows through the conductor from below, and the Ampere force directed from the sheet acts upward on it. This can happen if the north pole of a bar magnet is brought up...
a) on the left b) on the right;
c) from the front side of the sheet; d) on the reverse side of the sheet.
One of the advantages of pulse metal detectors is the ease of manufacturing search coils for them.. At the same time, with a simple coil, pulse metal detectors have a good detection depth. This article will describe the simplest and most affordable ways to make search coils for pulsed metal detectors with your own hands.
Coils made by the manufacturing methods described below, suitable for almost all popular schemes of impulse metal detectors (Koschei, Clone, Tracker, Pirate, etc.).
From a twisted pair wire, you can get an excellent sensor for pulse metal detectors. Such a coil will have a search depth of more than 1.5 meters and have good sensitivity to small objects (Coins, rings, etc.). To make it, you need a twisted pair wire (such a wire is used for an Internet connection and is on sale in any market and computer store). The wire consists of 4 twisted pairs of wires without screen!
The sequence of manufacturing a coil for a pulsed metal detector, from a twisted pair wire:
When testing such a coil with Koschey 5I metal detectors, the following data were obtained:
Here we describe the method production of a deep coil 50 * 70 cm, for impulse metal detectors. Such a coil is well suited for finding large metal targets at great depths, but it is not suitable for finding small metal.
winding a coil of copper wire, its mass increased by 17.8 g, and the resistance turned out to be 34 ohms. Estimate the length and cross-sectional area of \u200b\u200bthe wire from these data?
3. An ammeter and a resistor with a resistance of 2 ohms were connected in series to a current source with an internal resistance of 1 ohm. At the same time, the ammeter showed 1 A. What will the ammeter show if a 3 ohm resistor is used?
4. In the circuit, the voltmeter shows 3V, and the ammeter 0.5 A. With a current of 1A, the voltmeter shows 2.5 V. What are the EMF and internal resistance of the source?
5. A force of 6N acts on a charge of 3C in an electrostatic field. What is the field strength?
a.18 n/k b.0.5 n/k c.2n/k d 24 n/k e.there are no correct answers
6. How will the strength of the electric field of a point charge transferred from vacuum to a medium with a dielectric constant equal to 81 change?
a. will increase by 9 times b. will decrease by 9 times c. will increase in 81 d. will decrease by 81 times e. will not change
10. When moving an electric charge between points with a potential difference of 8 V, the forces acting on the charge from the electric field did the work of 4 J. What is the magnitude of the charge?
a.4 class b.32 class c.0.5 class d.2 class e.no correct
11. Charge 2cl moves from a point with a potential of 10 V to a point with a potential of 15 V. What work does the electric field do in this case?
a.10 j b.-10 j c.0.4 j d.2.5 j e. no correct
12. When a charge of 3 cells moves from 1 point to another, the electric field does 6 J of work. What is the potential difference between these points?
a.18 C b.2C c.0.5C d.9 E. no correct
13. How will the capacitance of a capacitor change when a dielectric with a permittivity of 2 is removed from it?
1) Determine the resistance of the heating element of the electric furnace, made of constantan wire with a cross-sectional area of 1 mm insquare and 24.2m long. 2) The 20 m extension cable is made of copper wire with a diameter of 1.2 mm. What is the resistance of the extension cord? What is the voltage drop across it if a current of 10 A flows through it?
1) Determine the resistance of the heating element of the electric furnace, made of constantan wire with a cross-sectional area of 1mm2 andlength 24.2m
2) 20 m long extension cable made of copper wire with a diameter of 1.2 mm. What is the resistance of the extension cord? what is the voltage drop across it if a current of 10A flows through it
Electrical wiring is made of copper wire 200 m long and 10 mm^2 in cross section. What is its resistance? What section should be chosenFor a gasoline internal combustion engine, the ignition system is one of the determining ones, although it is difficult to single out any main unit in a car. You can’t go without a motor, but it’s also impossible without a wheel.
The ignition coil creates a high voltage, without which it is impossible to spark and ignite the fuel-air mixture in the cylinders of a gasoline engine.
To understand why there is a reel in a car (this is a popular name), and what part it takes in ensuring movement, one must at least generally understand the design of ignition systems.
A simplified diagram of the bobbin operation is shown below. 
The positive terminal of the coil is connected to the positive terminal of the battery, and the other terminal is connected to the voltage distributor. This connection scheme is classic and is widely used on cars of the VAZ family. To complete the picture, a number of clarifications need to be made:
Mechanical devices were used in old cars: on the VAZ 2106 and the like, but now they are almost completely replaced by electronic ones.
The modern bobbin is a simplified version of the Ruhmkorff induction coil. It was named after the inventor of German origin - Heinrich Ruhmkorff, who was the first to patent in 1851 a device that converts a constant low voltage into an alternating high voltage.
To understand the principle of operation, you need to know the structure of the ignition coil and the basics of radio electronics. 
This is a traditional, common VAZ ignition coil, used for a long time on many other cars. In fact, this is a pulse high-voltage transformer. A secondary winding is wound on a core designed to amplify the magnetic field with a thin wire; it can contain up to thirty thousand turns of wire.
Above the secondary winding is the primary of a thicker wire and with fewer turns (100-300).
The windings are interconnected at one end, the second end of the primary is connected to the batteries, the secondary winding is connected to the voltage distributor with its free end. The common winding point of the coil is connected to a voltage switch. The whole structure is covered by a protective case.
A direct current flows through the "primary" in the initial state. When a spark needs to be generated, the circuit is broken by a switch or distributor. This leads to the formation of high voltage in the secondary winding. Voltage is supplied to the spark plug of the desired cylinder, where a spark is formed, causing the combustion of the fuel mixture. High-voltage wires were used to connect the spark plugs to the distributor.
The single terminal design is not the only one possible, there are other options. 
The main parameter by which the performance of the bobbin is determined is the resistance of the windings. There are average indicators that indicate its serviceability. Although deviations from the norm are not always an indicator of a malfunction.
Using a multimeter, you can check the ignition coil by 3 parameters:
Please note that only the individual ignition coil can be tested in this way. Dual ones are arranged differently, and you need to know the output scheme of the “primary” and “secondary”.
We check the primary winding by attaching the probes to contacts B and K.
When measuring the "secondary", we connect one probe to contact B, and the second to the high-voltage output.
The insulation is measured through terminal B and the coil housing. The instrument readings must be at least 50 Mohm.
It is far from always that a simple motorist has a multimeter at hand and experience in using it; on a long journey, checking the ignition coil in this way is also not available.
Another way, especially relevant for old cars, including VAZs, is to check the spark. To do this, the central high-voltage wire is placed at a distance of 5-7 mm from the motor housing. If a blue or bright purple spark jumps when you try to start the car, the bobbin is working properly. If the color of the spark is lighter, yellow, or it is absent altogether, this may serve as confirmation of its breakdown or wire malfunction.
There is an easy way to test the system with individual coils. If the engine is troit, you just need to turn off the power to the coils one by one while the engine is running. The connector was disconnected and the sound of the work changed (the machine started to double) - the coil is in order. The sound remained the same - the spark does not enter the candle in this cylinder.
True, the problem may be in the candle itself, so for the purity of the experiment, you should swap the candle from this cylinder with any other.
If during dismantling you did not remember and did not note which wire went to which terminal, the ignition coil connection diagram is as follows. The terminal with the + sign or the letter B (battery) is powered by the battery, the switch is connected to the letter K. The colors of the wires in cars can vary, so it's easiest to track which one goes where.
The correct connection is important, and in the event of a polarity violation, the reel itself, the distributor, and the switch can be damaged.
One of the important components in the car is the bobbin, which creates a high voltage to form a spark. If failures appear in the engine, it starts to triple and just work unstably - the reason may be in it. Therefore, it is important to know how to check the ignition coil correctly, and if necessary, using the old-fashioned method, in the field.
For more than half a century of the evolution of carburetor gasoline engines with a contact ignition system, the coil (or, as drivers of past years often called it, “reel”) has practically not changed its design and appearance, representing a high-voltage transformer in a metal sealed glass filled with transformer oil to improve insulation between turns of windings and cooling.
An integral partner of the coil was a distributor - a low voltage mechanical switch and a high voltage distributor. The spark should have appeared in the respective cylinders at the end of the compression stroke of the air-fuel mixture - strictly at a certain moment. The distributor carried out both the generation of a spark, and its synchronization with the cycles of the engine, and distribution by candles.
The classic oil-filled ignition coil - "reel" (which in French meant "coil") - was extremely reliable. It was protected from mechanical influences by the steel glass of the body, from overheating - by effective heat removal through the oil filling the glass. However, according to the little-censored rhyme in the original version, “It was not about the reel - the idiot was sitting in the cab ...”, it turns out that a reliable reel sometimes failed, even if the driver was not such an idiot ...
If you look at the diagram of the contact ignition system, you can find that the muffled motor could stop in any position of the crankshaft, both with the contacts of the low voltage breaker in the distributor closed and open. If, during the previous shutdown, the engine stopped in the crankshaft position, in which the distributor cam closed the contacts of the breaker that supplied low voltage to the primary winding of the ignition coil, then when the driver, for some reason, turned on the ignition without starting the engine, and left the key in this position for a long time, the primary winding of the coil could overheat and burn out ... For a direct current of 8-10 amperes began to pass through it instead of an intermittent pulse.
Officially, the coil of the classic oil-filled type is not repairable: after the winding burned out, it was sent to the scrap. However, once upon a time at car depots, electricians managed to repair reels - they flared the case, drained the oil, rewound the windings and reassembled ... Yes, there were times!
And only after the mass introduction of contactless ignition, in which the distributor contacts were replaced by electronic switches, the problem of coil combustion almost disappeared. Most switches provided for automatic shutdown of the current through the ignition coil when the ignition was on, but the engine was not running. In other words, after the ignition was turned on, a small time interval began to count down, and if the driver did not start the engine during this time, the switch automatically turned off, protecting both the coil and itself from overheating.
The next stage in the development of the classic ignition coil was the rejection of the oil-filled housing. "Wet" coils were replaced by "dry". Structurally, it was practically the same coil, but without a metal case and oil, coated on top with a layer of epoxy compound to protect it from dust and moisture. She worked in conjunction with the same distributor, and often on sale one could find both old “wet” coils and new “dry” coils for the same car model. They were completely interchangeable, even the “ears” of the mounts matched.
For the average car owner, there were essentially no advantages or disadvantages in changing the technology from wet to dry. If the latter, of course, was made with high quality. "Profit" was received only by manufacturers, since it is somewhat easier and cheaper to make a "dry" coil. However, if the "dry" coils of foreign car manufacturers were initially thought out and manufactured quite carefully and served almost as long as the "wet" ones, the Soviet and Russian "dry" coils gained notoriety, because they had a lot of quality problems and failed quite often without any reason.
One way or another, today “wet” ignition coils have completely given way to “dry”, and the quality of the latter, even of domestic production, is practically not satisfactory.
There were also hybrid coils: an ordinary “dry” coil and a conventional contactless ignition switch were sometimes combined into a single module. Such designs were found, for example, on single-injection Fords, Audis and a number of others. On the one hand, it looked to some extent technologically advanced, on the other hand, reliability decreased and the price increased. After all, two fairly heating nodes were combined into one, while individually they cooled better, and if one or another failed, the replacement was cheaper ...
Oh yes, even in the piggy bank of specific hybrids: on old Toyotas, there was often a variant of a coil integrated directly into the distributor of the distributor! It was integrated, of course, not tightly, and in the event of a failure, the “reel” could be easily removed and purchased separately.
A noticeable evolution in the coil world occurred during the development of injection motors. The first injectors included a “partial distributor” - the low-voltage circuit of the coil was already switched by the electronic engine control unit, but the classic runner distributor, driven by the camshaft, was still distributing the spark through the cylinders. It became possible to completely abandon this mechanical unit by using a combined coil, in the common body of which individual coils were hidden in an amount corresponding to the number of cylinders. Such nodes began to be called "ignition modules".
The electronic engine control unit (ECU) contained 4 transistor keys, which alternately applied 12 volts to the primary windings of all four coils of the ignition module, and they, in turn, sent a high-voltage spark pulse each to their own candle. Simplified versions of combined coils are even more common, more technologically advanced and cheaper to manufacture. In them, in one housing of the ignition module of a four-cylinder engine, not four coils are placed, but two, but working, nevertheless, for four candles. In such a scheme, a spark is supplied to the candles in pairs - that is, it comes to one candle from a pair at the moment necessary to ignite the mixture, and to the other - idle, at the moment the exhaust gases are released from this cylinder.
The next stage in the development of combined coils was the transfer of electronic switching keys (transistors) from the engine control unit to the ignition module housing. The removal of powerful and heating transistors “to the wild” improved the temperature regime of the computer, and if any electronic switch-key failed, it was enough to replace the coil, and not change or solder the complex and expensive control unit. In which immobilizer passwords, individual for each car, and similar information are often registered.
Another typical ignition solution for modern gasoline cars, which exists in parallel with modular coils, is individual coils for each cylinder, which are installed in the spark plug well and contact the spark plug directly, without a high-voltage wire.
The first "personal coils" were just coils, but then switching electronics moved into them - just as it happened with ignition modules. Of the advantages of this form factor is the rejection of high-voltage wires, as well as the ability to replace only one coil, rather than the entire module, if it fails.
True, it is worth saying that in this format (coils without high-voltage wires mounted on a candle) there are also coils in the form of a single block, united by a common base. Such, for example, like to use GM and PSA. This is a truly nightmarish technical solution: the coils seem to be separate, but if one “bobbin” fails, you have to change the assembly of a large and very expensive unit ...
The classic oil-filled bobbin was one of the most reliable and indestructible units in carbureted and early injection cars. Sudden failure of it was considered a rarity. True, its reliability, unfortunately, was "compensated" by an integral partner - a distributor, and later - an electronic switch (the latter, however, only applied to domestic products). The “dry” coils that replaced the “oil” coils were comparable in terms of reliability, but still failed somewhat more often for no apparent reason.
Injection evolution forced to get rid of the distributor. This is how various designs appeared that did not need a mechanical high-voltage distributor - modules and individual coils according to the number of cylinders. The reliability of such structures has decreased even more due to the complication and miniaturization of their "offal", as well as the extremely difficult conditions of their work. After several years of operation with constant heating from the engine on which the coils were mounted, cracks formed on the protective layer of the compound, through which moisture and oil entered the high-voltage winding, causing breakdowns inside the windings and misfiring. With individual coils that are installed in candle wells, working conditions are even more hellish. Also, gentle modern coils do not like washing the engine compartment and the increased gap in the electrodes of the spark plugs, which is formed as a result of the long-term operation of the latter. The spark is always looking for the shortest path, and often finds it inside the winding of the bobbin.
As a result, today the most reliable and correct design of the existing and used ones can be called an ignition module with built-in switching electronics, mounted on an engine with an air gap and connected to spark plugs by high-voltage wires. Less reliable are separate coils installed in the candle wells of the head of the block, and, from my point of view, the solution in the form of combined coils on a single ramp is completely unsuccessful.
