3. Answer the questions:

1. What are ammeters?

2. What are voltmeters?

3. What are wattmeters?

4. Is a voltmeter connected in parallel across the point of a circuit?

5. What is the main difference between the two instruments of the same type?

6. What is the calibration of a voltmeter? Ammeter?

4. Imagine that you are a teacher of electrotechnics and your students ask you about measuring devices.

Make up a dialogue and try to explain all you know about them.

5. Translate the following expressions into Ukrainian:

• Of the same type or design

• Identical moving units

• To be used for either meter

• Positive or negative lead

• Otherwise the reading would be incorrect

• Is to be measured

• Consumed by it

• A drop of potential

• Across the circuit

• The instantaneous values

Unit 13.

ELECTROMAGNETIC WAVES

1. Read and translate the text: electromagnetic waves

Radio waves, light, X-rays, and some cosmic rays — they all belong to the same family. They travel at the velocity of light. The wave has both electric and magnetic components which are bound together. At the end of its travel the wave gives up energy. The ether waves are those we know as wireless waves.

When the waves are too long they are "seen" as infra-red, when they are too short they are "seen" as ultra-violet. Shorter than the ultra-violet are X-rays and far shorter than the shortest of these are the "gamma" rays, and finally the cosmic rays.

The penetrative power of these increases as the wave length decreases.

To sum up: all these electromagnetic waves travel through the ether at the same enormous speed; the different effect which they produce depends entirely upon their length. Some more words about ultra-violet and X-rays. Ultra-violet rays are familiar to most people as the particular art of sunlight that is "health-giving".

The effect of the ultra-violet rays is to produce in the skin the vitamin that is important for the promotion of bone-growth. The use of these rays in diagnosis is a powerful weapon of medicine. One of the most valuable uses of ultra-violet rays in industry is the testing of the quality of certain goods. X-raying is very important in metallic welding. X-rays were discovered by Rontgen after whom the rays are sometimes called. The discovery of X-rays was quickly followed by its application to medicine.

2.Remember the words and expressions:

• Radio waves - радіохвилі

• X-rays – рентгенівські промені

• Cosmic rays – космічні промені

• Velocity of light – швидкість світла

• Wireless waves - радіохвилі

• Infra-red – інфра-червоні

• Ultra-violet- ультрафіолет

• Bone-growth – ріст кісток

• Metallic welding- зварювання металу

• Powerful weapon – сильна зброя

• Rontgen – Рентген

3. Make up a dialogue about the Electromagnetic Waves. Use the following expressions:

• They all belong to the same family;

• Gives up;

• Far shorter than the shortest of these;

• To sum up;

• Depends entirely upon their length;

• Are familiar to most people;

• After whom;