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Unit 15 - Part A
- Module
- Physics Applied Science
- Institution
- PEARSON (PEARSON)
An in depth essay on Electrical circuits that got a distinction.
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NameUnit 15: Electrical Circuits & Their Applications
Section 1 – AC and DC current
Alternating current is an electric current that occasionally reverses direction, as
opposed to direct current that flows in one direction only. Alternating current is the
type where electricity is supplied to businesses and households, and it is the form of
electricity that customers usually use when plugging kitchen appliances, televisions,
fans and electric lamps into a wall socket. Whilst, direct current (DC) is the movement
of an electric charge unidirectionally. A primary example of DC power is an
electrochemical cell. Direct current may flow through a conductor such as a wire but
may also flow through semiconductors, insulators, or even through a vacuum such as
in electron or ion beams. In a constant direction, the electric current flows, separating
it from the alternating current (AC).
A DC can be created in a variety of ways: The direct current can be created by an AC
generator fitted with a system called a "commutator." Usage of a "rectifier" system
that converts AC to DC. Batteries provide DC, which is produced within the battery by
a chemical reaction. On the other hand, an electric generator generates an alternating
current. When the wire rotates in the magnetic field, a force is generated by the
changing intensity of the magnetic field through the wire which drives the electrical
, Name
charges around the wire. At first the force produces an electric current along the wire
in one direction.
Section 2 – Effects of AC and DC electricity on the human
physiology
The bodies are not conductors,
they are insulators. Not much but
a bit of current will go through
which we can sense and have no
harm to us. But if a significant
quantity goes through our body
will get a shock and in a few
minutes we will instantly die. Ac
current is more harmful than dc
because the electrons flow in the
upper layer of wire which is
hazardous and can cause disaster
to a man who touches it. If
someone touches a dc current
then the dc current can push
through someone at a large
distance because in a dc phase it
does not change and moves along
x-axis.
Tests show that the internal resistance of the human body to the current ranges from
300 to 1000 ohms, and then the resistance of the human skin to the current ranges
from 1000 to 100,000 ohms, but when the resistance becomes wet then decreases.
The skin effect causes the conductor's effective resistance to increase at higher
frequencies where the skin depth is less, thus reducing the conductor's effective
cross-. The effect on the skin is due to opposing eddy currents caused by the
alternating magnetic field arising from the alternating current. Wet or broken skin will
reduce the resistance of the body to 1,000 ohms, adding that high-voltage electrical
energy breaks down human skin rapidly, reducing the resistance of the human body
to 500 ohms.
The extent of the electrical shock damage depends on the amount of electrical
current and the length of time that the current is flowing through the body. For
example, 1/10 of an ampere (amp) of electricity that passes through the body for just
2 seconds is sufficient to cause death. The amount of internal current that a person
can withstand and still be able to control arm and hand muscles can be lower than 10
milliamperes (milliamps or mA). Currents greater than 10 mA can paralyse or "freeze"
the muscles. When this "freezing" occurs, a person can't release a tool, wire, or other
object any longer. The electrified item may in reality be kept even closer, resulting in
longer exposure to the surprising current. Of this reason handheld tools can be very
dangerous, giving a shock. When you are unable to let go of the lever, the current can
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