3. Match items in column a) with items in column b).

a) b)

1) stiff a) field

2) oscillating b) output

3) magnetic c) current

4) rotor d) losses

5) stator e) rotor

6) adjacent f) ring

7) split ring g) pole

8) sparking h) coil

9) commutator i) section

10) friction j) commutator

11) motor k) brush

4. Put questions to the text. Motor types

SERVO MOTOR

Servo is an automatic device that uses error-sensing feedback to correct the performance of a mechanism. The term is applied only to systems where the feedback or error correction signals help to control mechanical position or other parameters. For example, an automotive power window control is not a servomechanism, as there is no automatic feedback which controls position; the operator does this by observation. But the car’s cruise control uses closed loop feedback, which classifies it as a servomechanism.

SYNCHRONOUS ELECTRIC MOTOR

A synchronous electric motor is an AC motor distinguished by a rotor spinning with coils passing magnets at the same rate as the alternating current. Contrast this with an induction motor, which must slip to produce torque. A synchronous motor is like induction motor except the rotor is excited by a DC field. Slip rings and brushes are used to conduct current to rotor. The rotor poles are connected to each other and move at the same speed.

ELECTROSTATIC (CAPACITOR) MOTOR

An electrostatic motor or capacitor motor is a type of electric motor based on the attraction and repulsion of electric charge. Usually electrostatic motors are the dual of conventional coil-based motors. They typically require a high voltage power supply, although very small motors employ lower voltages. Today the electrostatic motor finds frequent use in micro-mechanical systems where their drive voltages are below 100 volts, and where moving, charged plates are far easier to fabricate than coils and iron cores. Also, the molecular machinery which runs living cells is often based on linear and rotary electronic motors.

5. Complete the table using the information from the text and speak about different types of motors using the table.

   Type of motor	Construction	Application
   DC motor
   AC motor
   Brushless motor
   Brushed DC motor
   Servo motor
   Synchronous electric motor
   Electrostatic(capacitor) motor

6. Give the summary of the text. The Development of Electric Motor

The engine which can convert electric energy into mechanical was already in existence. As early as in 1822, M. Faraday outlined the way in which an electric motor could work: by placing a coil, or an armature between the poles of electromagnet; when a current is made to flow through the coil, the electromagnet force causes it to rotate the reverse principle, in fact, of a generator.

The Russian physicist, Jacobi built several electric motors during the middle decades of the XIXth century. Jacobi even succeeded in running a small, battery-powered electric boat on the Neva River in St.Petersburg. All of them, however, came to the conclusion that the electric motor was a rather uneconomical machine so long as galvanic batteries were the only source of electricity. It did not occur to them that motors and generators could be made interchangeable.

In 1888 Professor Galileo Ferraris in Turin and Nicola Tesla invented independently and without knowing of each other’s work, the induction motor. This machine, a most important but little recognized technical achievement, provides no less than two-thirds of all the motive power for the factories of the world, and much of modern industry could not work without it. Known under the name of squirrel-cage motor because it resembles the wire cage in which squirrels used to be kept – it has two circular rings made of copper or aluminum joined by a few dozen parallel bars of the same material, thus forming a cylindrical cage.

Although the induction motor has been improved a great deal and its power increased many times ever since its invention, there has never been any change of the underlying principle. One of its drawbacks was that its speed was constant and unchangeable.