Limitations of Ohm’s Law

The relationship between voltage and current is known as Ohm’s law. One of the fundamental laws used to study electric circuits and their potential differences is Ohm’s law. To put it another way, the voltage in a conductor is proportional to the current flowing through it.

For example, increasing the number of cells in a torch enhances the bulb’s brightness. When we use the torch for a long period, however, we notice that the bulb’s brightness progressively lowers.

Electric Current

A flow of particles (electrons) passing through wires and components is referred to as an electric current. It is the rate of charge flow. We say there is an electric current in a conductor when an electric charge travels through it. Electrons make up a charge flow in circuits that use metallic conductors.

In this case, the conventional direction of electric current is used instead of the direction of electron flow. If a charge Q travels across a conductor’s cross-section in time t, the current I, then current  I = Q/t. The coulomb is the SI unit of charge, and electric current is measured in coulomb per second, which is referred to as an ‘ampere.’ The current in the cell passes from the negative to the positive terminal.

Flow of Current

A force is experienced when a little amount of electric charge is deposited in the electric field due to another charge. As a result, action on the positive charge is required. The electric current in electrolytes and ionised gases is made up of both positively and negatively charged ions flowing around. When n electrons flow through a conductor’s cross-section in time t, the total charge passing through the conductor is Q = ne.

Ohm’s Law

The relationship between current, voltage, and resistance is described by Ohm’s law. The potential difference, or voltage, across a large number of materials is directly proportional to the amount of constant current flowing through them.

As a result, if the voltage V (in volts) between two ends of a wire made from one of these materials is tripled, the current I (amperes) triples as well, and the quotient V/I stays constant.

The resistance, R, of a given piece of material is defined as the quotient V/I, measured in ohms. The resistance of materials that obey Ohm’s law does not change over wide voltage and current ranges. 

V/I = R is a mathematical expression of Ohm’s law. By 1827, the German physicist Georg Simon Ohm’s investigations had shown that the resistance, or the ratio of voltage to current, for all or part of an electric circuit at a certain temperature is generally constant.

Graph of Ohm’s Law

A diagram can be used to represent the measured values. The voltage is plotted on the y axis, which is the vertical axis. We plot the current on the x axis, which is the horizontal axis. Because it depicts the relationship between voltage and current, this graph is termed a voltage-current graph.

We can now draw a straight line by connecting the measured data points. When a straight line appears on a plot, we say the displayed quantities are linearly connected to one another. As a result, we’ve discovered that voltage and current are linearly connected. And this is exactly what Ohm’s law says.

Limitation of Ohm’s Law

• As unilateral electrical elements like diodes and transistors only allow current to flow in one way, Ohm’s law does not apply to them.

• Voltage and current will not be constant with respect to time for nonlinear electrical elements with properties such as capacitance, resistance, and so on, making Ohm’s law problematic to apply. Non-linear elements have current that is not proportional to the applied voltage, which means that the resistance of those elements varies depending on the voltage and current. The thyristor, electric arc, and other non-linear elements are examples.

• The sign of V (+ or -) affects the relationship between V and I. In other words, if I is the current for a given V, reversing the direction of V while maintaining its magnitude does not result in a current of the same magnitude as I in the other direction. This can happen in the case of a diode, for example.

• Only metallic conductors are subject to Ohm’s law. As a result, it will not function with non-metallic conductors.

Application of Ohm’s Law

The voltage applied in a circuit, the resistance value, and the current flowing through the circuit may all be determined using Ohm’s law. We can determine the value of other parameters such as resistivity and many more using the above three values. Ohm’s law is used in the following ways on a daily basis:

In fuses

Fuses and circuit breakers are used to protect a circuit. The electrical appliances are linked in series with these. The value of the current that could travel through the fuses can be determined using Ohm’s law. If the current amount is too high, it might damage the circuit and even cause the electronic gadget to explode.

To Know Power consumption

The electrical heaters contain a high-resistance metal coil that permits a specific amount of current to pass through it in order to generate heat. The power to be given to the heaters is determined using this law.

To Control the speed of the fan

We can control the speed of the fans in our homes by moving the regulator from start to end. The current going through the fan is regulated here by regulating the resistance via the regulator. Using Ohm’s Law, we can determine the resistance, current, and consequently power flowing for any given input value.

Conclusion

In this article we have studied about electric Current and about Ohm’s Law. The relationship between current, voltage, and resistance is described by Ohm’s law. The potential difference, or voltage, across a large number of materials is directly proportional to the amount of constant current flowing through them.

The voltage applied in a circuit, the resistance value, and the current flowing through the circuit may all be determined using Ohm’s law.