Basics for EEE & ECE Students - 1

Q:- What is a linear element

In an electrical network, a linear element shows the linear characteristics in between voltage & current. That is the current passing through a linear element is changed according to the change in the voltage across its terminals.

An important phenomenon of any linear element is the properties of the linear element do not change with the change of applied voltage or the circuit current. Resistors, inductors, capacitors are linear elements as their resistances, inductances, capacitances do not change with a change in applied voltage or the circuit current.

A circuit which is made with only linear elements, is called linear network. Sometime this type of circuit is very useful where voltage versus current relationship should remain linear & any signal distortion is not required.
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2Q:- What is a nonlinear element?

In an electrical network, a non-linear shows the non-linear characteristics in between voltage & current. More specifically, in case of a non-linear element the current passing through it does not change linearly with the linear change in applied voltage at a particular frequency.

An important phenomenon of any non-linear element is they can can distort a given signal. As, they shows non-linear characteristics in between voltage & current so, their current versus voltage curve is not a straight line.

As a instance, we can say a transistor is a non-linear element as the current through it is a non-linear function of the voltage across its terminals. Actually, vacuum tubes, semiconductor devices like diodes, transistors are the non-linear elements.
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3Q:- What is a unilateral element ?

Suppose, an electrical element is connected with a voltage source. If the element is unilateral, then whenever there is a change is occurred in the polarity of the applied voltage, that is the positive & negative terminal of the source altered, the magnitude of the current passing through the element is affected by the polarity change.

Think about a simple diode, which is connected with a voltage source. If somehow the polarity is changed, that is the (+) & (−) terminal interchanged, then the diode will not work. So, we can say, diode is an unilateral element. A important feature of an unilateral element is, it offer varying impedances with variations in flow of current.

Basically, semiconductor devices like diodes, transistors, operational amplifiers are the unilateral element.
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4Q:- What is a bilateral element

Suppose, an electrical element is connected with a voltage source. In case of a bilateral element, if any change occurred in the polarity of the applied voltage, the magnitude of the current passing through the element is not affected by that polarity change.

Lets make it simpler. Think " a " terminal is the positive terminal & terminal " b " is negative terminal of any voltage source. If the legs of a bilateral element altered their position, then the current through it will not affected.

Think about a simple resistor, which is connected with a voltage source. If somehow the polarity is changed, that is the (+) & (−) terminal interchanged, then the current passing through it does not affected, that is the resistor still in same working condition.

A important feature of the bilateral element is, it offers the same impedance irrespective of direction of flow of current. A resistor or a light bulb is the example of bilateral element.
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5Q:- What is electric charge?

We generally hear about the terms 'positive charges', 'negative charges'. These two types of charges are present in the nature. The classification of charges comes from a very simple logic. The electric charge and the nature of charge is determined by the electrons. The loosely bonded electrons from the outer layer of an atom are pretty easy to de touch. Sometimes for matters with high electro negativity, excess electrons can attached with its atom. Depending on this, the nature and magnitude of charge can be determined. Now if there is extra electron in the matter then that can be termed as negatively charged. Because, the charge of electron is negative that means presence of extra electrons make a matter negatively charged. Similarly if there are no extra electrons, the matter is not charged at all and if there is deficiency of electrons, i.e electrons of outer layers have de touched, then there are more protons compared to electrons. So, the matter becomes positively charged.

Electrons and protons are considered as elementary charges. Their electric charge is 1.602 × 10⁻¹⁹ coulombs and for electrons, this is negative and for protons this is positive. Now, two negatively or two positively charged matters repels each other, whereas there is attraction between two different types of charged matters. The intensity of the attraction or repletion force is determined by the amount of charge in the matter.
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