Resistance Formula Overview
R = V I is the resistance formula. Resistance is the measure of any object's opposition to the flow of electric current. A resistor is an electrical component that provides a defined amount of resistance in a circuit. Resistance is the property of materials that permits electric current to flow. Resistance obviously opposes the flow of a stream. In addition, the resistance unit is ohms, which is represented by the Greek capital letter omega (Ω).
Resistance Formula Key Terms with SI Units
|
Terms |
Symbols |
Meaning |
SI Units |
|
Ohm |
Ω |
The electrical resistance unit. SI units of kg. m². s3. A² |
- |
|
Resistor |
- |
A device that reduces the current flow. |
- |
|
Resistivity |
p |
The amount by which a certain substance opposes current flow. |
The SI unit of resistivity is Ω.m |
|
Ampere |
A |
The current is required to transmit one coulomb of charge per second. |
- |
|
Resistance |
R |
The amount of a thing opposes the current flow. It is determined by the material, length, and cross-sectional area. |
The SI unit of electric resistance is Ohm (Ω). |
|
Direct Current |
DC |
Charge is always flowing in one direction. |
- |
|
Current |
I |
The amount of charge that travels through a specific region over time. |
The SI unit of current is the ampere (A). |
What is Resistance?
Resistance is the property of materials that permits electric current to flow. The movement of the stream is surely opposed by resistance. The passage of electrons is referred to as electric current.
For example- A person struggling to move from one shop to another in a crowded market. This condition is quite similar to an electron attempting to pass through a wire.
Furthermore, the resistance unit is ohms, which is symbolized by the Greek capital letter omega. Furthermore, the resistance is affected by the voltage across a resistor as well as the current running through it. Resistance is a measure of the resistance to current flow in a certain electrical circuit.
An object's electrical resistance is the measure of its resistance to the flow of electric current. The electrical conductance is the inverse quantity. Electrical conductance refers to the ease with which an electrical current may be passed. Furthermore, electric resistance has some similarities with mechanical friction. In addition, resistors are electrical circuit components. To some extent, all of the materials hinder current flow.
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Resistance to Electricity
The inverse of mechanical resistance is electrical resistance, which is the resistance supplied by a circuit to the free passage of current. In a circuit, resistance operates similarly to friction. Like friction, electrical resistance inhibits the flow of electricity across a wire in the same manner that friction opposes free and easy motion.
Resistance Derivation
|
V = IR, according to Ohm's Law |
The same current passes through each resistor when three resistors are linked in series, but the voltage drop varies. If V is the applied voltage and the voltages across the resistances R1, R2, and R3 are V1, V2, and V3, respectively, then
V = V1+V2+V3... (1)
According to Ohm's rule, V = IR
Req = R1+R2+R3
As a result, the circuit's equivalent resistance or total resistance may be defined as a single value of resistance that can replace any number of resistors linked in series without altering the current or voltage value of the circuit. The generalized formula for equivalent resistance, if we have n series resistances, is
Req = R1+R2+R3.......+Rn
We already know that the voltage supplied is (v).
Therefore,
V = V1+V2+V3 ∴V = V1+V2+V3
We also know that
V = IR (according to Ohm's law)
Therefore,
IReq = IR1+IR2+IR1
⇒ IReq = I(R1+R2+R3) ⇒IReq = I(R1+R2+R3)
⇒ R1+R2+R3
As a result, the equivalent resistance or total resistance of the circuit may be described as a single resistor value linked in series with varying current or voltage values in the circuit.
Students can read more about the Magnetic Effects of Electric Current and Father of Physics.
Electric Resistance Formula
There are two ways of determining the electrical resistance of a circuit. The first is the basic electric resistance formula.
R = l/A
It indicates the resistivity of the material in the aforementioned formula. L denotes the conductor's length, and A denotes the area of the cross-section of the wire or conductor you've been given. This is the primary formula for estimating any given conductor's electrical resistance.
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Ohm's law is another formula for calculating the electrical resistance of a given system. Ohm's law is a well-known practical physics law. If the temperature is constant, the current flowing through a circuit is directly proportional to the voltage put across it and inversely proportional to the resistance given by the wire, according to Ohm's law. Ohm's law is written down as a formula.
V = IR
|
Also read more about What is Friction and Dimension of Resistance.
Factors influencing Resistance
The electrical resistance of a conductor is governed by the following factors-
- The conductor's cross-sectional area
- The conductor's length
- The conductor's substance and the temperature
- Electrical resistance is related to conductor length (L) and inversely proportional to cross-sectional area (A).
- The following connection makes it feasible.
R = L/A
where is the resistivity of the substance (measured in ohms meter).
Students can read more about the Surface Tension and Refractive Index Formula.
Difference between Resistance and Resistivity
The following table tells the difference between resistance and resistivity-
|
Particulars |
Resistivity |
Resistance |
|
Definition |
The electrical resistance is provided per unit length and unit cross-sectional area at a given temperature. |
When the movement of electrons in a substance is resisted, resistance arises. |
|
Symbol |
p |
R |
|
Formula |
P = E/J |
R = V/I |
|
SI Unit |
Ohms. meter |
Ohms |
|
Dependance |
Temperature |
It is determined by the length and cross-sectional area of the conductor, as well as the temperature. |
Things to Keep in Mind
- A simple circuit is made up of a single voltage source and one resistance.
- One formulation of Ohm's law asserts that in a simple circuit, the relationship between current I, voltage V, and resistance R is I = V R.
- Resistance is measured in ohms and is proportional to volts and amperes by 1 = 1 V/A.
- The voltage or IR drop caused by current passing through a resistor is given by V = IR.
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Solved Examples of the Resistance Formula
Example 1- Determine the resistance when connections 5 and 2 are made in parallel.
Ans.The following are examples of resistances-
R1 = 5 Ω
R2 = 2 Ω
The parallel resistance is articulated as,
(R1R2) / (R1+R2)
=1.428 Ω
Example 2- A resistor in an electric circuit conducts a current of 4.00 A. The voltage drop between one end of the resistor and the other occurs to be 120 V. What is the importance of resistance?
Ans. Making use of the resistance formula,
R = VI
Therefore, R = 120V/4A
R = 30 Ω
As a result, the resistor in the circuit has a resistance of 30 Ω.
Example 3- In an electric circuit, a current of 6.00 A is flowing through a resistor. The voltage drop across the resistor from one end to the other is 150 V. What is the value of resistance?
Ans.As we know the current and voltage drop across the conductor, we can use Ohm's law to calculate the resistance as follows-
R = VI
By putting the values in the above equation, we obtain
R = 150V / 6A
R = 25 Ω
Therefore, the resistor's resistance in the circuit is 25 Ω.