Common rheostats include sliding rheostats and ?

Resistance box: A sliding rheostat can gradually change the resistance of the connected circuit, which plays a role in continuously changing the current magnitude, but it cannot accurately know the resistance value of the connected circuit. If you need to know the resistance value of the resistor connected to the circuit, you need to use a resistance box.

Figure A shows a plug-type resistance box, with a row of copper blocks on the cover of the resistance box, and a jack between the copper blocks, and a copper plug inserted into the hole. There are resistive wires connected between the two adjacent copper blocks under the jack. When the plug is inserted into the hole, two adjacent blocks of copper are connected together, and the current passes through the block.

When the copper plug is pulled out, the current passes through the resistive wire under the jack. The more copper plugs are pulled out, the greater the resistance to the circuit. The resistance values of the resistance wires under each jack are marked next to the jacks.

As long as the values next to the jacks without copper plugs are added together, it is the resistance value of the access circuit. Figure B shows that the resistance values of the access circuit are 1 ohm, 2 ohms, and 3 ohms.

The figure shows a schematic diagram of the knob resistance box, which has two binding posts on the panel, and several knobs, and the words "magnification" 1, 10, 100, and 1000 are marked next to the knobs, and the knobs are marked with a total of ten numbers from 0 to 9. When using the value pointed by the logo (white dot) on the panel and multiplying it by the magnification marked next to the knob, it is the resistance value of the circuit connected to the knob. The resistance box shown in the figure can be composed of various integer resistance values in the range of 0-9999 ohms for use in experiments, as shown in the figure, where the resistance value is 2408 ohms.

(1) Protection circuit.

2) Change the magnitude and direction of the current in the circuit by changing the resistance of the access circuit part, so as to change the voltage at both ends of the conductor (electrical appliance) connected in series. When connecting the sliding rheostat, it is required: "one up and down, the focus is on the bottom", and the metal rod and resistance wire each use a binding post; The actual connection should be selected according to the requirements of the two binding posts of the resistance wire.

3) Change the voltage. Ohm's law, which plays a role in changing the voltage at both ends of the electrical appliance in series with it.

4) Use voltammetry to measure resistance.

From "one picture and four uses", we talk about the role of sliding rheostats.

There are four very important experiments in junior high school physics and electricity:

1) The relationship between the current on the resistor and the voltage at both ends.

2) The relationship between the current and the resistance in the conductor.

3) Voltammetry resistance measurement experiment.

4) Experiment of measuring the electric power of small bulbs.

Teaching methods for the topic: contrastive pedagogy. From the aspects of experimental principles and methods, experimental precautions, and the role of sliding rheostats, the four experiments are compared and taught on the basis of the same circuit diagram, which is more conducive to the study of the rest of his life to distinguish the knowledge points and knowledge chain of this part. Distinguish the different emphases and precautions of each experiment; Review and consolidate the use of sliding rheostats, ammeters, and voltmeters.

Among them, the role of the sliding rheostat is the difficulty of students' learning, and it is also an important test point for the high school entrance examination.

According to my experience, the similarities and differences between the functions of the sliding rheostat in these four experiments are listed as follows:

Similarities: 1. Protection circuit. 2. By changing the size of the resistance in the sliding rheostat access circuit, change the distribution of the voltage at both ends of the resistor (or small bulb), and then change the size of the current in the circuit.

Differences: 1. In the experiment, the role of the sliding rheostat focuses on: by changing the voltage at both ends of the small bulb, the voltage value and the corresponding current value in multiple circuits are obtained, so as to use multiple sets of experimental data, the relationship between the current on the resistor and the voltage at both ends.

2. In the experiment on the relationship between the current and the resistance in the conductor, the function of the sliding rheostat focuses on: using the control variable method to control the wide state, the voltage at both ends of the control resistor is unchanged, and multiple groups of resistance values and corresponding current values are obtained, which are used for the relationship between the current and the resistance in the conductor when the voltage is constant.

3. The function of the sliding rheostat in the voltammetry resistance measurement experiment focuses on: changing the voltage at both ends of the resistor, changing the current in the circuit, obtaining the measured value of multiple resistances, and using the method of taking the average value of multiple measurement results to reduce the experimental error.

4. The function of the sliding rheostat in the experiment of measuring the electric power of the small bulb focuses on: changing the voltage at both ends of the small bulb so that it is in the real amount of u, u, u

In the case of u real u forehead, observe the brightness of the small bulb and realize the u forehead

According to the indication of voltmeter and ammeter, the actual electric power corresponding to the small bulb is obtained, and then the relationship between the actual electric power and the brightness of the small bulb is compared.

An electronic component that can be adjusted to obtain different resistances.

This is a device that can adjust the size of the resistor, and the amount of current can be adjusted when connected to the circuit. Generally, a rheostat consists of a wire with a high resistance and a device that can change the contact point to adjust the effective length of the resistance wire.

Sliding rheostat construction:1Terminal.

2.Slides. 3.Porcelain tubes.

4.Coil. 5.Metal rods.

The resistance wire of the sliding rheostat is wound around an insulating porcelain cylinder, and the resistance wire is coated with an insulating layer on the outside.

The sliding rheostat is a resistive element with adjustable resistance value made of alloy wire with large resistivity wound on an insulated porcelain tube.

Hope it helps.

The magnitude of the current is changed by changing the length of the resistance line of the access circuit.

The teacher said oh, I'm in the third year of junior high school.

The sliding rheostat consists of a porcelain cylinder, a coil, a metal rod, a binding post and a metal sheet.

Sliding rheostat:

Principle: Change the length of the electric annihilation band resistance line in the access circuit to change the resistance.

Purpose: Change the current and voltage in the circuit by changing the resistance in the access circuit.

Nameplate: For example, a sliding rheostat marked with "50 2A" means that the maximum resistance is 50, and the maximum allowable current is 2A.

Answer: The travel structure of the sliding rheostat generally includes five parts, such as a binding post, a sliding blade, a resistance wire, a metal rod and a porcelain cylinder, and the sliding rheostat is an important element in the circuit, which changes its own resistance by moving the position of the sliding blade, so as to play the role of protecting the circuit and controlling the circuit. Related Extensions:

The sliding rheostat is an important component in the belt Chang circuit, which changes its resistance by moving the position of the sliding blade, so as to play the role of protection circuit and control circuit. The composition of the sliding rheostat generally includes five parts: binding post, sliding vane, resistance wire, metal rod and porcelain cylinder. In circuit analysis, a sliding rheostat can be used either as a fixed-value resistor or as a variable-value resistor.

The resistance wire of the sliding rheostat is generally a nickel-chromium alloy with a high melting point and large resistance, and the metal rod is generally a metal with a small resistance, so when the resistance cross-sectional area is constant, the longer the resistance wire, the greater the resistance, and the shorter the resistance wire, the smaller the resistance.

1.Just look at the connection of the rheostat in the circuit.

I found a simple circuit diagram with a rheostat, hoping to help understand.

2.The brightness of the bulb is directly determined by its actual power, the greater the power, that is, the greater the work done per unit time, the greater the brightness.

How it works.

Sliding rheostat is one of the commonly used devices in electricity, and its working principle is to change the resistance by changing the length of the resistance line of the access circuit part, so as to gradually change the current in the circuit. The resistance wire of the sliding rheostat is generally a nickel-chromium alloy with a high melting point and large resistance, and the resistance rod is generally a metal with small resistance, so the longer the resistance wire, the greater the resistance, and the shorter the resistance rod, the smaller the resistance. The main purpose of this paragraph.

(1) Protection circuit. That is, before connecting the circuit and closing the electric bond, the sliding blade p of the sliding rheostat should be adjusted so that the resistance of the sliding rheostat connected to the circuit part is maximized. (2) Change the current in the circuit by changing the resistance of the access circuit part, thereby changing the voltage at both ends of the conductor (electrical appliance) connected in series.

There should be an arrow in the circuit diagram. Underneath is a rectangle. There is a line connected to the rectangle. If the arrow is close to that line, it becomes smaller. Otherwise, it will become bigger. The brightness of the bulb is determined by the actual voltage.