In this article, you will be able to understand, what is resistance or electrical resistance in a circuit, and the unit of resistance that is the ohm. We will also discuss resistivity and how resistance is measured through an ohm meter.
Resistance Definitions
·
Resistance is the property of a material to
block or tends to block the flow of electrons.
·
The ability of a material to oppose the flow
of electrons or electricity is called resistance.
·
The characteristic property of a material to
show opposition to the flow of electrons passing through it.
·
Resistance is the measure of the opposition
to the flow of current in a circuit.
Unit
In the system international, the unit of resistance is
called the ohm.
Ohm
It is represented by a Greek letter “Ω” called
omega. Ohm is named in Honor of Georg Simon Ohm (1784-1854), was a German
physicist, who observed the relationship between current, voltage, and
resistance.
According to Ohm’s law,
Current
= Voltage / Resistance
Resistance
= Voltage / Current
or,
R =
V / I
Ohm
= Volt / Ampere
Ω = V
/ A
So,
One ohm is defined as the resistance of a circuit or
material when one-ampere current is transferred through it by applying one
volt of potential difference to that material.
What is resistance in a circuit?
One of the main characteristics of
electronic circuits is their ability to conduct electricity. Conductors such as
aluminum and copper allow electrical current to pass freely through them.
However, non-conductive materials such as plastic or wood block the movement of
current. Some circuits have resistances that make it difficult for electricity
to pass through, which is called resistance. Every circuit has resistances that
make it difficult for electricity to pass through. Resistance is a concept that
can be difficult to understand, so we will explain its uses and how it works
mathematically.
Each circuit has resistances that
make it difficult for electricity to pass through. Resistance is a property of
electric circuits that causes current to slow down and generates heat when
current passes through it. Bodies of resistance are made up of material
objects; these objects slow down the movement of current and create heat when
electricity passes through them. The more material objects are placed in a
circuit, the more heat is produced and the slower the passing of current
becomes. Therefore, careful placement of circuit components is necessary to
produce the desired results.
Every circuit has resistances that
make it difficult for electricity to pass through. Resistance is a property of
electric circuits that causes current to slow down and generates heat when
current passes through it. Bodies of resistance are made up of material
objects; these objects slow down the movement of current and create heat when
electricity passes through them. The more material objects are placed in a
circuit, the more heat is produced and the slower the passing of current
becomes. Therefore, careful placement of circuit components is necessary to
produce the desired results.
Electronic devices use many
different types of resistance to perform various functions. Resistors are used
in analog circuits as part of hand-tuning circuits and amplifiers. They are also
used in digital logic as memory devices and as controls for microprocessors in
computers and cell phones. Overall, resistors provide us with a multitude of
ways to customize our electronic devices!
Resistance is an essential concept
in all types of circuits. It allows us to customize our electronic devices by selecting
suitable materials for construction and components for different values of
resistance. Resistance is an inherent property of all matter; hence, no matter
what type of circuit we construct, there will always be some degree of
resistance present within the material object from which the circuit derives
its name.
Ohm meter
It is a device that is used to measure the resistance
of a circuit, material, or component by physically connecting its terminals to
the circuit to be measured.
It can also tell us how much
resistance is in a circuit.
Multimeters can also perform as ohmmeters when it is set in resistance-measuring mode. An ohmmeter supplies a small current to the circuit or component whose resistance is to be measured. It then measures the resulting voltage by calculating the resistance using Ohm’s law.
When the power source is present or active in a circuit or the circuit is carrying a current, an ohmmeter should not be connected to that circuit. Before connecting the ohmmeter, power should be disconnected from the circuit. Ohmmeters can work either connected in series or parallel based on requirements.
A small electrical current is used by an ohm meter to check the continuity of a circuit. However, you can also use an ohmmeter to observe continuity in motors, cables, and fuses. If the circuit is closed or is open.
The approximate value of resistance is given by an ohm meter.
It is also used in the laboratory and is a portable device. There are three types
of ohm meters, they are the series ohmmeter, shunt ohmmeter, and
multi-range ohmmeter.
Resistivity
It is the property of a particular material,
which opposes the flow of charges or current passing through it.
The resistance per unit length and the
cross-sectional area of a material is called its
resistivity.
Resistivity is represented by a Greek letter “ρ” called rho.
Unit
As the laws of resistance show,
Resistance is directly proportional to the length of the
conductor and inversely proportional to the cross-sectional area of the conductor.
It means that, when the length of the conductor is
increased, the resistance is also increased and, when the length of the
conductor is shortened, the resistance is decreased, and so the current flow
easily.
Similarly, when the cross-sectional area of the conductor
is increased, due to its inverse proportion to the resistance, the resistance is
decreased, and the resistance is increased while reducing in cross-sectional
area.
Mathematically,
Resistance
∝ Length / Cross-sectional
Area
R ∝ L / A
R = ρ L / A
Where ρ is the constant of proportionality and is called
resistivity.
ρ = R A / L
ρ
= Ω m2
/ m
ρ
= Ω m
So, the Ohm-meter is the unit of resistivity.
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