Understanding Ohm's Law: Resistor Behavior At Certain Volts

Ohm's law states that the electric current through a conductor between two points is directly proportional to the voltage across the two points. In other words, it describes the relationship between current and voltage for a specific class of electrical objects. A resistor that functions according to Ohm's law is called an Ohmic resistor, and it introduces resistance to the flow of electric current in a circuit. The voltage drop across the terminals of an Ohmic resistor is proportional to the magnitude of resistance. The rate of flow of electrical charge, or electric current, through an electrical resistor is proportional to the difference in voltage measured across the resistor.

Resistors are passive elements that introduce resistance to the flow of electric current in a circuit

Resistors are passive electrical components that introduce resistance to the flow of electric current in a circuit. They are used to limit or reduce the flow of electric current and are found in almost all electrical networks and electronic circuits. The resistance offered by a resistor is measured in ohms (Ω).

Ohm's law states that the current is proportional to the voltage across the terminal ends of a resistor. This means that if you know the voltage and resistance, you can calculate the current using Ohm's law. Similarly, if you know the current and resistance, you can find the voltage. This relationship between voltage, current, and resistance is fundamental to understanding how resistors work.

The primary function of a resistor is to limit or control the flow of electric current. This is achieved by introducing a specific amount of resistance into the circuit. The amount of resistance depends on the application and is specified by the electrical engineer. Resistors can be fixed or variable. Variable resistors, the most common type, can be adjusted to a specific ohmic value within a certain range, while fixed resistors have a predetermined resistance value.

Resistors work by deliberately losing energy in the form of heat or thermal energy. This property is utilized in appliances such as electric heaters, ovens, and toasters, where the heat generated by the resistor is used to warm the surrounding area. Even the filament in an incandescent light bulb is a form of resistor, slowing down the current and heating up the wire until it emits light.

In addition to their use in heating applications, resistors are also essential in the proper functioning of electronics. They help ensure that other components in a circuit do not receive too much voltage or electric current. Resistors are used for various purposes, including limiting electric current, voltage division, heat generation, matching and loading circuits, gain control, and setting time constants.

Ohm's law is not universally valid

Ohm's law holds for circuits containing only resistive elements, for all forms of driving voltage or current, regardless of whether the driving voltage or current is constant (DC) or time-varying (AC). When reactive elements such as capacitors, inductors, or transmission lines are involved in a circuit to which AC or time-varying voltage or current is applied, the relationship between voltage and current becomes the solution to a differential equation, and Ohm's law does not directly apply.

Ohm's law states that the current flowing through a conductor is directly proportional to the potential difference applied across its ends, provided all physical conditions and temperatures remain constant. In certain components, increasing the current raises the temperature, and Ohm's law cannot be applied. For example, the filament of a light bulb, in which the temperature rises as the current is increased.

Elements that follow Ohm's law are called ohmic elements, and those that do not are called non-ohmic elements. Some examples of non-ohmic elements are germanium, tungsten, semiconductor diodes, vacuum tubes, liquid electrolytes, and LEDs.

The resistance of a network of resistors arranged in series

A resistor is a passive element that introduces resistance to the flow of electric current in a circuit. When resistors are arranged in a series, the total resistance (RT) is the sum of the individual resistances. This means that the current must pass through each resistor, and it experiences the resistance of each.

For example, consider three resistors with resistances R1, R2, and R3 connected in series. The total resistance, RT, of the circuit is equal to the sum of the individual resistors: RT = R1 + R2 + R3. This logic extends to any number of resistors in series. So, if there are four resistors, R4 would be added to the equation, and so on.

The same current passes through each resistor in a series, but the voltage across each resistor is proportional to its resistance. Using Ohm's Law, where V = IR, the voltage drop across each resistor can be calculated. For instance, if a current of 1A is passed through the above circuit, the voltage drop across R1 would be 1V if R1 = 1Ω.

Resistors in series can be replaced by a single equivalent resistor, REQ, or impedance, ZEQ. This is true regardless of the complexity of the series resistor network. All resistors in a series will obey the same basic rules as defined by Ohm's Law and Kirchhoff's Circuit Laws.

It is important to note that the total resistance of any two or more resistors connected in series will always be greater than the value of the largest resistor in the chain. For example, if the largest resistor in the above example is 6kΩ, the total resistance, RT, will be greater than this value.

Additionally, the series-parallel network can be formed by connecting resistors in parallel sets of series networks or series sets of parallel networks. This can significantly increase the total power-handling capacity of the network compared to a single parallel resistor.

The resistance of a network of resistors arranged in parallel

A resistor is a passive element that introduces resistance to the flow of electric current in a circuit. An Ohmic resistor is one that functions according to Ohm's law, which states that the voltage drop across the terminals is proportional to the magnitude of resistance. The unit for resistance is the ohm, where 1Ω = 1 V/A.

Ohm's law is not universally valid, but it does hold for many substances, including good conductors like copper and aluminium, and some poor conductors under certain circumstances. These substances are called ohmic. Ohmic materials have a resistance R that is independent of voltage V and current I.

Now, when resistors are connected in parallel, more current flows from the source than would flow for any of them individually, so the total resistance is lower. This is because, by adding another resistor in parallel, we have opened up a new channel through which more current can flow. The total current flowing from the power supply will be at least slightly higher than the current through a single resistor.

The voltage drop across all of the resistors in a parallel resistive network is the same. This is because each resistor is subject to the same potential difference (voltage), and the currents through them add. The inverse of the equivalent resistance is equal to the sum of the inverse resistance of all the resistors in the network.

The equivalent resistance of a combination of resistors depends on both their individual values and how they are connected. In a parallel circuit, all of the resistor leads on one side of the resistors are connected together, and all the leads on the other side are connected together. Each resistor has the same potential drop across it, and the currents through each resistor may be different, depending on the resistor. The sum of the individual currents equals the current that flows into the parallel connections.

Calculating the equivalent resistance of resistors in parallel by hand can be tiresome, but there are online calculators that can help.

The resistance value in ohms is often marked with a colour code on the resistor

A resistor is a passive element that introduces resistance to the flow of electric current in a circuit. A resistor that functions according to Ohm's law is called an Ohmic resistor. When current passes through an Ohmic resistor, the voltage drop across the terminals is proportional to the magnitude of the resistance.

Resistors with six bands are usually high-precision resistors with an additional band to specify the temperature coefficient. The most common colour for the sixth band is brown, which indicates a temperature coefficient of 100 ppm/˚C. This means that for every 10˚C change in temperature, the resistance value changes by 1000 ppm or 0.1%.

It is important to note that the reading direction of the colour code may not always be clear. Sometimes, the increased space between bands 3 and 4 can indicate the reading direction, with the first band usually being the closest to a lead. It is good practice to check the manufacturer's documentation to be sure of the colour coding system used. In some cases, measuring the resistance with an ohmmeter may be the only way to determine the resistance, such as when the colour bands are burnt off.

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