Resistance is the opposition offered by a material to the flow of electric current. It is caused by collisions between electrons and atoms in the material, converting electrical energy into heat.
\(R = \frac{V}{I}\)
Longer conductors have higher resistance.
Thinner conductors offer more resistance.
Higher temperatures increase resistance in most materials.
Different materials have varying resistivity values.
Resistance is used to generate heat in devices like toasters, heaters, and incandescent light bulbs.
Resistors are used to divide voltage in circuits, enabling specific voltage levels.
Resistors control current flow and prevent damage in electronic circuits.
They’re used in electronics to modify signal amplitudes and shapes.
Resistors in fuses and surge protectors prevent excessive current flow.
Certain resistive materials change resistance with temperature, light, or pressure, making them useful in sensors.
The method of connect the electric components is called circuit. There are two types of circuits,
In a series combination of resistors, resistors are connected end to end, so the same current flows through each resistor.
Let suppose three resistors R1, R2, and R3 are connected in series. When this combination is connected to a battery of V volts, it draws current I from the battery. R1 is a single resistor. This resistor is such that when it is connected to the same battery of V volts, it also draws current from the battery. By applying Ohm’s law to each resistor, we have:
V₁ = IR₁
V₂ = IR₂
V₃ = IR₃
V = IR
Using them in the equation we get:
IR = IR₁ + IR₂ + IR₃
IRe = I(R₁ + R₂ + R₃)
Re = R₁ + R₂ + R₃
Series combinations are useful when specific voltage drops are required or when using multiple resistors to achieve a desired total resistance. However, the increase in total resistance can impact overall circuit performance.
In a parallel combination of resistors, the resistors are connected across the same two points, allowing the same voltage to be applied across each resistor.
Let suppose three resistors R₁, R₂, and R₃ are connected in parallel. When this combination is connected to a battery of V volts, it draws current I from the battery. Re is a single resistor. This resistor is such that when it is connected to the same battery of V volts, it also draws current I from the battery. This resistor is therefore called the equivalent resistor and its resistance is called equivalent resistance.
I = V / R
where V is the voltage across the circuit and R is the equivalent resistance.
Applying Ohm’s law to each resistor, we have:
V₁ = IR₁
V₂ = IR₂
V₃ = IR₃
where V₁, V₂, and V₃ are the voltages across resistors R₁, R₂, and R₃, respectively.
Summing these equations, we get:
V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃)
or
V = IR₁ + IR₂ + IR₃
Dividing both sides by V, we get:
1 = 1/R₁ + 1/R₂ + 1/R₃
or
R = 1/Re = (1/R₁ + 1/R₂ + 1/R₃)
This shows that the equivalent resistance of a resistor is equal to the sum of the reciprocals of individual resistances.
Parallel combinations are useful when maintaining voltage consistency is important or when multiple resistors need to achieve a lower total resistance. However, complex calculations and potential variations in voltage distribution should be considered.