Basics For EEE and ECE Students - 3

Q:- Explain Ohm’s law

One the most important & fundamental laws of electronics is the ohms law. This law defines the relationships between current, voltage and resistance. A good way to understand ohms laws is an analogy with a domestic water system.

Thinking how? Let’s see:

Let’s start with the terms present in the definition:

• V = voltage: The easiest way to think of voltage is to call it potential. We know the potential is something which is very useful to do work. Imagine two tanks of water connected with a pipe. If one tank of water is placed higher than the other then there is potential for water to flow from the high level tank to the low level tank. This water pressure is similar to that used to drive electricity around a circuit, called the potential difference, this is measured in volts. This potential difference is provided by a battery or in the case of huge electricity a generator at the generating station.

• I = current: As the water flows through the pipe in a water system due to potential difference ,in the same way an electric current flows through a copper wire. So, current is simply the transfer of something from one place to another. The standard unit of electric current is one ampere that is the current produced by a one volt source in a circuit having a resistance of one ohm.

• R = resistance: Resistance meaning anything that opposes the flow of current. In this case of two tanks of water connected by a pipe, imagine resistance is formed by the pipe. As the pipe gets wider, more water flows & as the pipe gets narrower, less water flows. If there were no pipe between the two bodies of water, we can say there is infinite resistance. The unit by which electrical resistance is measured is Ohm & one ohm is equal to the current of one ampere which will flow when a voltage of one volt is applied.

Now that you got the concept ohm, volt and ampere, so now it’s the time to introduce you to the relationship in between them that is ohms law. The statement is, the electric current passing through a conductor is directly proportional to the potential difference across it, provided that the temperature remains constant. The constant of proportionality is the resistance of the conductor.

The definition above simply states that the current passing through a conductor increases if you increase the voltage.

So, we can say: V proportional to I

Thus, V = IR, Where , V = potential difference in volts (V)

I = current in amps (A) and

R = the constant of proportionality that is the resistance.
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2Q:- What is Ohm’s Law?

Before defining ohms law let us first discuss about the electrical resistance. Electrical resistance is the property of a material by virtue of which it opposes the flow of electrons through a material i.e. conductor. Thus, resistance restricts the flow of electric current through the metallic conductor. The unit of resistance is ohm (Ω), which is obtained from ohms law .

Ohm's law states that physical condition being unchanged , the current through any conductor is directly proportional to the applied potential difference across it.

It can be expressed as V ∝ I

or, V = R × I

Here R is the constant of proportionality and is termed as resistance .

Therefore we an get R = V / I

Applications and limitations of of ohms law:

Ohms law is applicable for any bilateral circuit . It cannot be used for any unilateral network i.e circuits consisting of transistors, diodes etc.Elements which obey ohms law are called ohmic or linear elements . This law is not applicable for non linear elements ie thyristors.
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