UNIT I ELECTRICAL CIRCUITS
DC Circuits
Prerequisites:
A DC circuit (Direct Current circuit) is an electrical circuit that consists of
any combination of constant voltage sources, constant current sources, and
resistors. In this case, the circuit voltages and currents are constant, i.e.,
independent of time. More technically, a DC circuit has no memory. That is, a
particular circuit voltage or current does not depend on the past value of any
circuit voltage or current. This implies that the system of equations that represent
a DC circuit do not involve integrals or derivatives.
Introduction:
In electronics, it is common to refer to a circuit that is powered by a DC voltage
source such as a battery or the output of a DC power supply as a DC circuit even
though what is meant is that the circuit is DC powered.
If a capacitor and/or inductor is added to a DC circuit, the resulting circuit is not,
strictly speaking, a DC circuit. However, most such circuits have a DC solution.
This solution gives the circuit voltages and currents when the circuit is in DC
steady state. More technically, such a circuit is represented by a system of
differential equations. The solution to these equations usually contains a time
varying or transient part as well as constant or steady state part. It is this steady
state part that is the DC solution. There are some circuits that do not have a DC
solution. Two simple examples are a constant current source connected to a
capacitor and a constant voltage source connected to an inductor.
Electro-magnetic force(E.M.F):
Electromotive Force is, the voltage produced by an electric battery or
generator in an electrical circuit or, more precisely, the energy supplied by a
source of electric power in driving a unit charge around the circuit. The unit is
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,the volt. A difference in charge between two points in a material can be created
by an external energy source such as a battery. This causes electrons to move so
that there is an excess of electrons at one point and a deficiency of electrons at a
second point. This difference in charge is stored as electrical potential energy
known as emf. It is the emf that causes a current to flow through a circuit.
Voltage:
Voltage is electric potential energy per unit charge, measured in joules
per coulomb. It is often referred to as "electric potential", which then must be
distinguished from electric potential energy by noting that the "potential" is a
"per-unit-charge" quantity. Like mechanical potential energy, the zero of
potential can be chosen at any point, so the difference in voltage is the quantity
which is physically meaningful. The difference in voltage measured when
moving from point A to point B is equal to the work which would have to be
done, per unit charge, against the electric field to move the charge from A to B.
Potential Difference:
A quantity related to the amount of energy needed to move an object from one
place to another against various types of forces. The term is most often used as
an abbreviation of "electrical potential difference", but it also occurs in many
other branches of physics. Only changes in potential or potential energy (not the
absolute values) can be measured.
Electrical potential difference is the voltage between two points, or the voltage
drop transversely over an impedance (from one extremity to another). It is related
to the energy needed to move a unit of electrical charge from one point to the
other against the electrostatic field that is present. The unit of electrical potential
difference is the volt (joule per coulomb). Gravitational potential difference
between two points on Earth is related to the energy needed to move a unit mass
from one point to the other against the Earth's gravitational field. The unit of
gravitational potential differences is joules per kilogram.
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,Electromagnetism:
When current passes through a conductor, magnetic field will be generated
around the conductor and the conductor become a magnet. This phenomenon is
called electromagnetism. Since the magnet is produced electric current, it is called
the electromagnet. An electromagnet is a type of magnet in which the magnetic
field is produced by a flow of electric current. The magnetic field disappears when
the current ceases. In short, when current flow through a conductor, magnetic
field will be generated. When the current ceases, the magnetic field disappear.
Applications of Electromagnetism:
Electromagnetism has numerous applications in today's world of science
and physics. The very basic application of electromagnetism is in the use of
motors. The motor has a switch that continuously switches the polarity of the
outside of motor. An electromagnet does the same thing. We can change the
direction by simply reversing the current. The inside of the motor has an
electromagnet, but the current is controlled in such a way that the outside magnet
repels it.
Another very useful application of electromagnetism is the "CAT scan
machine." This machine is usually used in hospitals to diagnose a disease. As we
know that current is present in our body and the stronger the current, the strong
is the magnetic field. This scanning technology is able to pick up the magnetic
fields, and it can be easily identified where there is a great amount of electrical
activity inside the body
The work of the human brain is based on electromagnetism. Electrical
impulses cause the operations inside the brain and it has some magnetic field.
When two magnetic fields cross each other inside the brain, interference occurs
which is not healthy for the brain.
Ohm’s Law
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, Ohm's law states that the current through a conductor between two points is
directly proportional to the potential difference or voltage across the two points,
and inversely proportional to the resistance between them. The mathematical
equation that describes this relationship is:
I = V/R
where I is the current through the resistance in units of amperes,
V is the potential difference measured across the resistance in units of
volts,
and R is the resistance of the conductor in units of ohms.
More specifically, Ohm's law states that the R in this relation is constant,
independent of the current.
AC Circuits
Prerequisites:
An alternating current (AC) is an electrical current, where the magnitude of the
current varies in a cyclical form, as opposed to direct current, where the polarity
of the current stays constant.
The usual waveform of an AC circuit is generally that of a sine wave, as
this results in the most efficient transmission of energy. However in certain
applications different waveforms are used, such as triangular or square waves
Introduction:
Used generically, AC refers to the form in which electricity is delivered
to businesses and residences. However, audio and radio signals carried on
electrical wire are also examples of alternating current. In these applications, an
important goal is often the recovery of information encoded (or modulated) onto
the AC signal.
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DC Circuits
Prerequisites:
A DC circuit (Direct Current circuit) is an electrical circuit that consists of
any combination of constant voltage sources, constant current sources, and
resistors. In this case, the circuit voltages and currents are constant, i.e.,
independent of time. More technically, a DC circuit has no memory. That is, a
particular circuit voltage or current does not depend on the past value of any
circuit voltage or current. This implies that the system of equations that represent
a DC circuit do not involve integrals or derivatives.
Introduction:
In electronics, it is common to refer to a circuit that is powered by a DC voltage
source such as a battery or the output of a DC power supply as a DC circuit even
though what is meant is that the circuit is DC powered.
If a capacitor and/or inductor is added to a DC circuit, the resulting circuit is not,
strictly speaking, a DC circuit. However, most such circuits have a DC solution.
This solution gives the circuit voltages and currents when the circuit is in DC
steady state. More technically, such a circuit is represented by a system of
differential equations. The solution to these equations usually contains a time
varying or transient part as well as constant or steady state part. It is this steady
state part that is the DC solution. There are some circuits that do not have a DC
solution. Two simple examples are a constant current source connected to a
capacitor and a constant voltage source connected to an inductor.
Electro-magnetic force(E.M.F):
Electromotive Force is, the voltage produced by an electric battery or
generator in an electrical circuit or, more precisely, the energy supplied by a
source of electric power in driving a unit charge around the circuit. The unit is
www.BrainKart.com
,the volt. A difference in charge between two points in a material can be created
by an external energy source such as a battery. This causes electrons to move so
that there is an excess of electrons at one point and a deficiency of electrons at a
second point. This difference in charge is stored as electrical potential energy
known as emf. It is the emf that causes a current to flow through a circuit.
Voltage:
Voltage is electric potential energy per unit charge, measured in joules
per coulomb. It is often referred to as "electric potential", which then must be
distinguished from electric potential energy by noting that the "potential" is a
"per-unit-charge" quantity. Like mechanical potential energy, the zero of
potential can be chosen at any point, so the difference in voltage is the quantity
which is physically meaningful. The difference in voltage measured when
moving from point A to point B is equal to the work which would have to be
done, per unit charge, against the electric field to move the charge from A to B.
Potential Difference:
A quantity related to the amount of energy needed to move an object from one
place to another against various types of forces. The term is most often used as
an abbreviation of "electrical potential difference", but it also occurs in many
other branches of physics. Only changes in potential or potential energy (not the
absolute values) can be measured.
Electrical potential difference is the voltage between two points, or the voltage
drop transversely over an impedance (from one extremity to another). It is related
to the energy needed to move a unit of electrical charge from one point to the
other against the electrostatic field that is present. The unit of electrical potential
difference is the volt (joule per coulomb). Gravitational potential difference
between two points on Earth is related to the energy needed to move a unit mass
from one point to the other against the Earth's gravitational field. The unit of
gravitational potential differences is joules per kilogram.
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,Electromagnetism:
When current passes through a conductor, magnetic field will be generated
around the conductor and the conductor become a magnet. This phenomenon is
called electromagnetism. Since the magnet is produced electric current, it is called
the electromagnet. An electromagnet is a type of magnet in which the magnetic
field is produced by a flow of electric current. The magnetic field disappears when
the current ceases. In short, when current flow through a conductor, magnetic
field will be generated. When the current ceases, the magnetic field disappear.
Applications of Electromagnetism:
Electromagnetism has numerous applications in today's world of science
and physics. The very basic application of electromagnetism is in the use of
motors. The motor has a switch that continuously switches the polarity of the
outside of motor. An electromagnet does the same thing. We can change the
direction by simply reversing the current. The inside of the motor has an
electromagnet, but the current is controlled in such a way that the outside magnet
repels it.
Another very useful application of electromagnetism is the "CAT scan
machine." This machine is usually used in hospitals to diagnose a disease. As we
know that current is present in our body and the stronger the current, the strong
is the magnetic field. This scanning technology is able to pick up the magnetic
fields, and it can be easily identified where there is a great amount of electrical
activity inside the body
The work of the human brain is based on electromagnetism. Electrical
impulses cause the operations inside the brain and it has some magnetic field.
When two magnetic fields cross each other inside the brain, interference occurs
which is not healthy for the brain.
Ohm’s Law
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, Ohm's law states that the current through a conductor between two points is
directly proportional to the potential difference or voltage across the two points,
and inversely proportional to the resistance between them. The mathematical
equation that describes this relationship is:
I = V/R
where I is the current through the resistance in units of amperes,
V is the potential difference measured across the resistance in units of
volts,
and R is the resistance of the conductor in units of ohms.
More specifically, Ohm's law states that the R in this relation is constant,
independent of the current.
AC Circuits
Prerequisites:
An alternating current (AC) is an electrical current, where the magnitude of the
current varies in a cyclical form, as opposed to direct current, where the polarity
of the current stays constant.
The usual waveform of an AC circuit is generally that of a sine wave, as
this results in the most efficient transmission of energy. However in certain
applications different waveforms are used, such as triangular or square waves
Introduction:
Used generically, AC refers to the form in which electricity is delivered
to businesses and residences. However, audio and radio signals carried on
electrical wire are also examples of alternating current. In these applications, an
important goal is often the recovery of information encoded (or modulated) onto
the AC signal.
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