Exercise 1. Answer the questions

Exercise 1. Answer the questions

1. What is current?

2. What types of current do you know?

3. What type of current is called alternating current?

4. What type of current is called direct current?

5. What is the frequency of the current?

6. What device is used to transform AC power from one voltage to another?

7. Is it often necessary to change AC into DC?

 

Exercise 2. Choose the correct answer

1. DC is current that …           a) changes its direction of flow

b) flows in one direction

2. AC flows provided …         a) a direct voltage source is applied

b) an alternating voltage source is ap- plied

3. The 50 Hz alternating current

…

a) flows in one direction 50 times per se- cond

b) flows in one direction 50 times and in the other direction 50 times per second

4. AC …                                   a) can be changed into DC

b) cannot be changed into DC

 

 

Unit 3. Parallel and series circuits

Vocabulary

to add up                     складываться, суммироваться

to blow                        перегорать (об электроприборах)

to complete circuit     замыкать цепь

to connect                   соединять

to go out                      погаснуть

identical                      одинаковый, идентичный

milliampere, mA        миллиампер

mixed connection       смешанное соединение parallel connection                                    параллельное соединение series connection                                    последовательное соединение supply voltage                        напряжение питания

volt, V                         вольт (единица измерения напряжения, э.д.с.)

Text

There are two ways of connecting circuit components:

1. Connection in series

When components are connected in series each compo- nent has the same current.

The battery voltage is divided between the two lamps.

Each lamp will have half the battery voltage if the lamps are identical.

2.

Connection in parallel

When components are connected in parallel each component has the same voltage.

Both lamps have the full battery voltage across them.

The battery current is divided between the two lamps.

Most circuits contain a mixture of series and parallel connections. The terms series circuit and parallel circuit are sometimes used, but only the simplest of circuits are entirely one type or the other. It is better to refer to specific components and say they are connected in series or connected in

parallel.

For example, the circuit shows a mixed connec- tion: a resistor and LED are connected in series (on the right) and two lamps are connected in parallel (in the centre). The switch is connected in series with the

two lamps.