The choice of a way of inclusion of a rheostat in a chain is connected, as a rule, with purpose of this rheostat in the concrete scheme. Therefore is necessary - to understand the schematic diagram of the device which is used.
It is required to you
- The textbook in physics, a ball pen, the sheet of paper.
Instruction
1. Using the textbook in physics, repeat how current in cases of parallel and consecutive turning on of resistors in an electrical circuit is distributed. Knowledge of these regularities will allow to connect a rheostat correctly. It is known that at parallel connection of the resistor in a chain the current passing earlier through an element to which the resistor is connected is divided into two parts: one part flows through an initial element, and another – via the resistor.
2. Draw the scheme of parallel inclusion of a rheostat in a chain if you need to shunt some element of a chain and to control current through it in the greatest possible limits. At the greatest possible value of resistance of a rheostat the current through the studied element remains initial, and at the minimum resistance all current passes through a rheostat bypassing an element.
3. Pay attention that the scheme of parallel inclusion of a rheostat will not allow you to control the general current in a chain because at parallel connection of elements the general current does not change, it is only distributed between separate branches.
4. If you need to have an opportunity to change the general current of a chain, then the rheostat needs to be connected consistently with chain elements. Then there will be an opportunity to change the general resistance of a chain, regulating thus and the general current.
5. Notice that at connection of a rheostat consistently with the studied element there is an opportunity to increase and reduce tension on an element. It is proved by the fact that tension in a chain will be distributed on elements according to the rule: the more resistance, the is more tension falling on this element.
6. Pay also attention to what at connection of a rheostat in a chain consistently with the studied element it is possible to control not only tension on this element, but also current. At change of current in the general chain its value changes also in the separate elements of a chain included consistently in a chain. Meanwhile, there is a certain difference between two ways of regulation of current through an element. In case of connection of a rheostat consistently you have an opportunity to change current in the studied element, without mentioning all scheme, so, without interfering in an operating mode of the device. In case of inclusion of a rheostat consistently in an electrical circuit any manipulations with it lead to fluctuations of current in all chain, breaking, thus, operation of the device.