VI. Define the following terms.
Battery, alternating current, direct current, static electricity, electric current, wire, laboratory, terminal, electron.
Meters
Reading
I. Read the following words:
interaction, instrument, rotation, ammeter, voltmeter, galvanometer, similar, proportional.
I I. Read and translate the text.
Using Ohm’s Law and the law of the force of interaction between the magnet and the current, we can make very simple instruments to answer all these questions.
The ohmmeter is used to measure the value of resistance. It consists of a milliameter calibrated to read in ohms, a battery and resistors. The meter is connected in parallel and the circuit is not opened when its resistance is measured. The readings on the scale show the measured value.
The ammeter is used to measure the current flowing in an electric circuit. The greater the current in the coil, the greater the force and, therefore, the greater the angle of rotation of the armature. The deflection is measured by means of a pointer attached to the armature.
When the currents to be detected and measured are very small one should use a galvanometer. Some very sensitive galvanometers detect very small current.
voltmeter
is an instrument to be used for measuring the potential difference
between any two points in a circuit. Its action is similar to that of
an ammeter, both of them having armatures that move when an electric
current is sent through their coils. The deflection, like that of an
ammeter, is proportional to the current flowing through the armature
coil. In spite of all the similarity between a voltmeter and an
ammeter there are also important differences.
In addition to instruments for measuring current and voltage, there are also devices for measuring electric power and energy.
Vocabulary
III. Remember these words:
coil, armature, angle, to deflect, pointer, to attach, scale, to detect, device, meter, to measure, tiny, to calibrate.
IV. Read the following abbreviations.
V, W, h. p., km, kg, A, mA, d. с, а. с, gr, in, cm.
Grammar
V. Translate the following sentences paying attention to the infinitive.
A galvanometer is a sensitive instrument to detect and measure small electric currents.
The resistance of an iron conductor is found to exceed that of a copper one.
We know the atmosphere to extend several hundred kilometres above the earth.
The current is known to flow through a conductor in case there is a potential difference between the ends of the conductor.
One expects a voltmeter to have very high resistance.
Some energy must be expended to make the current flow or to maintain a potential difference at the conductor terminals.
To prove Ohm’s Law experimentally is not difficult at all.
To prove the connection between electricity and magnetism, one must point to the electromagnet.
VI. Find antonyms among the following words:
difficult, insulator, frequently, low, below, little, equal, seldom, high, easy, above, conductor, unequal, much.