23022 kotak ketahanan mengajar 0 ~ 9999.9 instrumen pengajaran fisika Eropa dan Tiongkok lima kenop peralatan eksperimental

单套产品重量（含小包装盒）   ：450g

单套产品重量（不含小包装盒）：400g

每箱40套

  Teaching resistance box

Instructions

1.Application:

The teaching resistance box, Model J2361, is suitable for the Laboratories of Middle Schools and Polytechnic Schools, the university students to carry on the following electricity experiments: Confirm Ohm’s law in part electric circuit; Expand the measuring range of Voltmeter by serving as the additional resistance; Measuring the unknown resistance; Adjust the current of requiring for known resistance to put in the circuit;  Measuring the electromotive force of the power source and internal resistance; etc. It’s the essential instrument in the electricity experiment.

2. Structure and application method

The teaching resistance box, Model J2361, uses the bakelite seal structure. The mode of  the resistance value converting is knob switch, it depends on the electronic brush to turn to the different positions to get the resistance value’s transformation. The arrangement of the board looks like Diagram 1, the line principle looks like Diagram 2. The resistor of the instrument uses the high stable, precise alloy manganese copper wire to circle on the porcelain bone shell with unfeeling. It goes through strict screening, examining, aging, dipping, the resistance value is stable and correct.

When using, it’s put in the circuit from the two wiring columns on the board. Adjust five knobs can obtain some resistance number between 0 to 9999.9Ω. The showing resistance value is added by the multiple of the reading number multiply it’s multiple above of each knob’s showing point. Generally the resistance value is the number which directs to each knob from the high multiple to the low one. Look at the Diagram 1, the resistance is 5083.2Ω.

3. Technical parameter

1). Accuracy rank: Ⅰ

2). Adjustable range of resistance value: 0~9999.9Ω,

     The minimum value: 0.1Ω

3). Application temperature: 0~40℃

4). Relative temperature:25%<80%

5). Zero position resistance: R₀<0.035Ω

6). Reference power :0.5W;     Rated power:1W

7). Volume: 165 x 125 x 60

8). Dielectric resistance between electric circuit to outer covering metal:>50MΩ

4. Example of experiment

1) Confirm Ohm’s law in part electric circuits:

Connect the resistance box, the button, the amperemeter, the slipped Rheostat and the power source together with the wire series, and then connect the voltmeter and the resistance box parallel, put on the power to adjust the current to the appropriate value. From the 

Amperemeter, the voltmeter and the resistance box’s reading number can get I=V/R.

2). Expand the measuring range of Voltmeter by serving as the additional resistance:

Connect the slipped Rheostat, the power and the voltmeter together like the Diagram. Put the power to the slipped Rheostat’s two fixed ends AC, then put one end of the voltmeter to the slipped touch-piece B, move B, make the voltmeter to full scale, write down the number of the voltmeter V₁, which is the voltage between A and B. Keep the slipped touch-piece motionless, connect the resistance and the voltmeter series, adjust the resistance’s value, make the reading number of the voltmeter reduce to some integer V₂, now the voltage between A and B does not change, but the measuring range of the voltmeter expand from original to n=V₁/V₂ times.

According to the resistance value and the original multiple of voltmeter’s expanding measuring range, can get the voltmeter’s resistance n.

N=R+r / r ( R is the reading number of the resistance box)

N=R / n-1

So according to the required multiple of expanding, can affix the different multiplier resistance.

R=(n-1)r

3）.use Substitute Method to measure the nuknow resistance of the circuit

use amperometer: distributary Current  Method or voltameter, distributary voltage Method to  measure the nuknow resistance.

circuit diagram is the following:

4). use resistance box as aware resistance  connectting into  circuit, use ,,,,to modify the needed current.

5). mesure the electromotive force and its inside resistance of power supply,circuit diagram is the following:  

connect the circuit,write down the data of  amperometer and voltameter (1);modify the  value of resistance box,write down the data of  amperometer and voltameter I2,R2;

    then use the function  we can get ,,,,

(2) experiment method  like the above function. calculational formula:

5.  Notice!

1:the MAX current cannot be more than the following data form in each rank.

2:resistance box should be saved in a room with air temperature 10-40,relative temperature <=,,,without polish air.

6. the failure and the mend of resistance box

1:reset resistance value  or its transformation is high.

2:the error of resistance box value is high.

3:resistance value is infinity,or some resistance loop are damaged.

The reason maybe is:the interface of  resistance box are damaged;

the circuit is  not clean or flexible;resistance loop are damaged;

You can do as the following:open the box clean.

when the circuit is turnoff  you must check the reason carefully.