Страница 14 (Text A) Упражнение 10 (Прочитайте текст)
Страница 15, упражнение 11 (ответьте на во по тексту ПОЛНЫМИ английскими предложениями)
Voltage and Current Characteristics of Resistors
The resistor is an electrical device whose primary function is to introduce resistance to
the flow of electric current. The magnitude of opposition to the flow of current is called the
resistance of the resistor. A larger resistance value indicates a greater opposition to current
flow. The resistance is measured in ohms. An ohm is the resistance that arises when a current
of one ampere is passed through a resistor subjected to one volt across its terminals. The vari-
ous uses of resistors include setting biases in p-n junction, controlling gain, fixing time con-
stants, matching and loading circuits, voltage division, and heat generation.
The resistance of a resistor is directly proportional to the resistivity of the material and
the length of the resistor and inversely proportional to the cross-sectional area perpendicular
to the direction of current flow. Resistivity is an inherent property of materials. Good resistor
materials typically have resistivities between 2 10-6 and 200 10-6 ·cm.
The resistance can also be defined in terms of sheet resistivity. If the sheet resistivity is
used, a standard sheet thickness is assumed and factored into resistivity. Typically, resistors
are rectangular in shape; therefore the length l divided by the width w gives the number of
squares within the resistor. The number of squares
multiplied
by
the
resistivity
is
the
resistance.
The resistance of a resistor can be defined
in terms of the voltage drop across the resistor and
current through the resistor related by Ohm’s law.
Whenever current is passed through a resistor, a
voltage is dropped across the ends of the resistor.
Ex. 11 Answer the questions to the text A:
1) What’s the primary function of a resistor?
2) How is the magnitude of opposition to the flow of current called?
3) What is an Ohm?
4) What are the characteristics of resistors?
5) What is shown in the scheme below?
ответ:1. The resistor is an electrical device whose primary function is to introduce resistance to
the flow of electric current.
2.The magnitude of opposition to the flow of current is called the
resistance of the resistor.
3.The resistance is measured in ohms. An ohm is the resistance that arises when a current
of one ampere is passed through a resistor subjected to one volt across its terminals.
Объяснение: