Английский язык. Громовая И.И - 82 стр.

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80
Another unlimited source of energy is the Sun. But at present only a small
part of solar energy is being used. Solar power station will permit to generate
cheap electricity in large quantities in the near future.
An enormous energy of the wind, exceeding millions of kilowatt-hours, has
not yet found effective application. Utilization of tidal energy has been studied
in many countries. Using tidal forces and wind energy will certainly make
considerable contribution to future electricity production.
(1605 t. un.)
Text 3. Properties of Electric Current and Electric Circuit
The flow of electrons through a circuit is called electric current. The strength
of the current depends on the rate at which electrons move in the conductor.
But we cannot see the effect produced by the electric current apart from
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the
conductor through which it flows. If a magnet is suspended near a conductor
carrying current, the magnet will deflect. Any piece of iron put near a conductor
will become magnetized. A body carrying electric current becomes magnetized.
Thus, to deflect a magnet, to magnetize iron and to heat the body are properties
of electric current.
The properties influencing the flow of electricity in the circuit are resistance,
inductance and capacitance.
Resistance is a property of a circuit to oppose the flow of electricity through
it. The resistance of a conductor to the flow of electric current depends on a
number of factors. First of all
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that is the material of the conductor. Different
materials offer different resistance to the flow of current. Metals generally
have resistance and are good conductors. Materials, which offer a very high
resistance, are used as insulators. Resistance is also affected by the length of
the conductor. The longer the conductor, the greater is the resistance. The unit
of resistance is the Ohm.
Inductance shows the ability of an electric current to create a magnetic
field. If the current is alternating, the magnetic field formed by this current
produces in the circuit the current of self-induction, which flows in the direction
opposite to that of the current in this electric circuit. Inductance depends on
the properties of the core and the structure of the coil. The unit of inductance
is the Henry.
Capacitance is the property of the electric circuit to store electricity. The
device designed to store electric charges is called a condenser or a capacitor.
The capacitance of that condenser depends on the area of the plates, the

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