Предмет: Алгебра, автор: kamilaa11

найдите уравнение окружности ,если ее радиус 9 см,а центр располагается в точке (-5,7)

Ответы

Автор ответа: Dmipasik

(x+5)^2+(y-7)^2 = 81
По общему правилу
Окружность радиуса R с центром в точке (a,b) имеет вид
(x-a)^2+(y-b)^2=R^2

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Предмет: Английский язык, автор: gravasamp

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Conductors.

1.Text.

According to their conductivity all materials are divided into conductors,

insulators and semiconductors. Conductors allow electricity to pass through

them; insulators do not.

Conductors are materials having a very high conductivity. A conductor owes its

conducting powers to the presence of free electrons which have broken away

from their atoms. The most common of them are metals (copper, aluminium,

steel, and others), carbon and electrolytes. Their coefficient of resistance is

different. Copper, for example, has a positive coefficient while carbon has a

negative coefficient of resistance.

According to their resistivity, conductors are divided into two groups; the first

includes materials with low resistivity; copper, aluminium and others. These

metals are used to produce wire conductors due to their high mechanical

strength. The second group includes materials with high resistivity: one of these is

nichrome. Due to its good heat resistance, nichrome is used to produce heaters.

Carbon is commonly used to produce electrodes and brushes for electric

machines.

3.Вопросы по тексту:

1. Into what groups are materials divided?

2. What do conductors do?

3. What materials are common conductors?

4. Are their coefficients of resistance different?

5. What metals have high mechanical strength?

6. What coefficient of resistance has carbon?

7. What materials are commonly used to produce wire conductors (brushes,

heaters)?

4.Переведите словосочетания:

a) wire strength; semiconducting material; air insulator- carbon brushes;

b) changing strength — changed resistance; insulating materials — insulated

conductors; heated brushes — heating sources.

c) common wire strength; highly conductive copper wire; commonly produced

wire brush; parallely connected circuit elements; commonly produced heaters.

d) any value of resistivity; rather low melting point.

5.Используйте в ответах: “certainly”, “I suppose”, “I don't know”.

1. Is bronze used to produce conductors?

2. Has copper a positive coefficient of resistance?

3. Have metals (steel, copper, iron) good mechanical strength?

6.Test. Choose the correct variant:

1. All materials are divided into ...

a) conductors and semiconductors;

b) conductors, insulators and semiconductors.

2. Copper has ...

a)high mechanical strength;

b)low mechanical strength.

3. Carbon has ...

a)a positive coefficient of resistance;

b)a negative coefficient of resistance.

4. Copper is commonly used to produce ...

a)heaters;

b)brushes.

7.Используйте английские слова вместо русских.

c) Any circuit (оказывает) resistance to the flow of current.

d) Resistance (зависит от) the temperature of the conductor.

e) Conductors are divided into groups (в зависимости от) their resistivity.