1: the solenoid electromagnetic coil skeleton cylinder diameter ca. 11 mm, ca. 80 mm, both ends of electromagnetic coil disc edge is about 8 mm wide, with cardboard cut, volume, viscosity and become, as shown inFigure 19.6 - 3. If there is a skeleton of the electromagnetic coil ready-made plastic or other materials, can also use the scale almost. With adiameter of about 0.5 mm of enameled wire, the skeleton of the electromagnetic coil lined around 1000 turns, and tap in the 300 turn and 600 turns. The iron core is about 1 cm in diameter, about 9 cm long soft iron rod (steel or iron screw corresponding scale may be used for general construction).

2 pointers with small magnetic disks: small, with two sections of scrap steel saw blade ca. 4 cm, magnetized in a bar magnet one-way conflictseveral times to make. A pointer is a length of about 40 cm of thebamboo needle, lower ca. 5 cm in a 6 x 6 mm 2 square, lower end of the longitudinal middle opening, two pieces of small magnetic clip (pole withto), and thread fastening. Pointers to other part, since the beginning ofthe round square cut, ca. 3 mm in diam gradually to the top, in order to make the center of gravity close to the small magnetic sheets as well. The use of a pin support bamboo needle make bamboo needle level balanceand then find the bamboo needle of the center of gravity. Clamp pin on the alcohol lamp put a pin is red hot, gravity center in bamboo needle topdirection about 5 mm (cone eye to burn, a few back cone penetrationcone ability after another) with a new pin through the bamboo needle, the eye of the top bar, put a pin into the appropriate range of risers, aspointer to a rolling shaft.

The 3 circuit: 10 - 12 volt DC power supply; 50 in Europe, 1.5 rheostat.Demonstration ammeter shunt in 1.5 Ann.

The 4 electromagnetic coils each parts of the device on the riser, shouldmake the switch on the circuit, solenoid and pointer small magnetsopposite ends of the same polarity, so that the small magnetic sheetsdismissed right, top left pointer. Switch S is connected with the cords ofthe crocodile clip, to easily with 300 turn, 600 turn 1000 turn the terminalis switched on or.

[Methods]

1 out of core, connect the 300 turn tap, conditioning sliding rheostat, can see the strength of the current increases with (or reduced), pointer deflection viewpoint also increase (or decrease). To clarify by solenoidmore strong, electromagnetic coil magnetic occurred more strong.

2 Changes on solenoid turns, with each change once conditioning sliding rheostat, the current show that the number of adhering to certain value(such as 0.5), the number of turns of solenoid sees more (or less),pointer deflection viewpoint is also bigger (or smaller). Clarify turns moreenergized solenoid, the magnetic more strong.

3 on 300 turn tap, current to 0.2 ANN, pointer deflection viewpoint is not big, but inserting core, then pointer deflection view increases obviously. Itclarifies the core by electromagnetic coil magnetization in the energizedsolenoid, the solenoid magnetic field greatly enhanced.

[note]

1 pointer shaft eye must cone is, there can be skewed around the upper and lower, to ensure that the pointer in the vertical scroll.

2 the demonstrator is made according to the principle of like poles repel.Because the same poles repulsion follow interval increases, so is not energized, the pointer at the lower end of the small magnetic sheets,should be as close as possible to the solenoid end, electricity, magneticrepulsive force will push away, both the interval increases, the repulsive force decreases. When the torque and the gravity repulsion on the entirepointer occurred restoring moment balance, pointer appears "stable equilibrium". Conversely, if the two are attractive, sheets and theinevitable demand of the solenoid apart a distance, then the suctionweak, but once the disk is sucked to move, both reduced, suctionincreases, until the disk is attracted to the solenoid recently far distance.In this way, the amount of change of the magnetic solenoid with currentsize, number of turns, core has no other factors affect, will be difficult toshow, so both must repel each other, this test will succeed.

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