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Unit 2.1 The basics of electricity
Page 59


20. Complete the text with the correct words.

ELECTROMAGNETISM

A solenoid is a coil of 1. wrapped in a 2. . When current flows through it, it generates a 3. field that induces 4. in wire when the magnet is moved 5. or 6. from it.
The field has two 7. (positive and negative). Its 8. depends on the amount of current flowing, whereas its 9. depends on the direction of the moving magnet.
21. Match the beginnings and endings.
attract or repel each other, according to their polarity.is called a solenoid.are surrounded by a positive or negative electric field.is related to the amount of current flowing.work according to the principles of electromagnetism.moving or stationary charges.the N and the S pole.by a changing magnetic field.were considered two distinct phenomena which were not related to each other.are attracted by magnets.generates a magnetic field.that surrounds every magnet.
Electricity is associated with... →
Electric charges… →
Two magnets can… →
Magnetic materials… →
Magnets have two poles, … →
A magnetic field is a force… →
Electricity and magnetism… →
The flow of current… →
The strength of a magnetic field… →
A cylinder made of wire wound in a series of loops… →
Current is induced in a wire… →
Electric motors, generators, and transformers… →
22. Fill in the sentences with the correct word. There are two words that you do not need to use.

generated • models • oscillator • metal • plastic • induces • search coil • delivered

Metal Detectors
Metal detectors are used to detect the presence of 1. objects by means of electromagnetic fields. There are different kinds of 2. , such as a walk through and a hand held. A typical metal detector mainly consists of a control box and a shaft containing a search coil. The control box is where the transmit signal is 3. and where the receive signal is processed. The 4. is used to transmit the electromagnetic field into the ground and to receive the return electromagnetic field from a metal object. The electromagnetic field is produced by an 5. , which is an electric circuit that can repeatedly switch on and off. If a metal object is found, the electromagnetic field 6. electric current to flow around the search coil, making a loudspeaker buzz.


Adapted from: https://www.azosensors.com/article.aspx?ArticleID=352