Network Theory Questions and Answers – Circuit Elements and Kirchhoff’s Laws

Circuit Elements and Kirchhoff’s Laws

1. Potential difference in electrical terminology is also known as _______

  1. Voltage
  2. Current
  3. Charge
  4. Conductance

Answer.1. Voltage

Explanation:-

Energy is required to move a charge from one point to another. Potential difference in electrical terminology is known as voltage, and is denoted by either V or v. Voltage is expressed in terms of energy (W) per unit charge (Q), i.e.

V = W/Q or v = dw/dq

Where

dw = small change in energy

dq = small change in charge

The energy (W) is expressed in joule (]), the charge (Q) is expressed in coulomb (C), and the voltage (V) is expressed in volt (V). The unit of voltage is volt.

1 volt = 1 joule/coulomb

 

2.  If the voltage-current characteristics is a straight line through the origin, then the element is said to be?

  1. Non-linear element
  2. Unilateral element
  3. Linear element
  4. Bilateral element

Answer.3. Linear element

Explanation

Linear circuit: The circuit whose parameters are constant, that is, they do not change with the application of voltage or current is called a linear circuit.

If the resistance, inductance or capacitance offered by an element does change linearly with the change in applied voltage or circuit current, the element is termed as linear element. The voltage-current characteristics is a straight line through the origin. Such an element shows a linear relation between voltage and current as shown in Fig.

Ordinary resistors, capacitors and inductors are examples of linear elements.

 

3. If the current does not change linearly with the change in applied voltage then it is called as

  1. Unilateral element
  2. Linear element
  3. Bilateral element
  4. Non-linear element

Answer.4. Non-linear element

Explanation-

Non-linear circuit: The circuit whose parameters change with the application of voltage or current is called a non-linear circuit.

A non-linear circuit element is one in which the current does not change linearly with the change in applied voltage. A semiconductor diode operating in the curved region of characteristics as shown in Fig. 1.28 is common example of non-linear element. Other examples of non-linear elements are voltage- dependent resistor (VDR), voltage-dependent capacitor (varactor), temperature-dependent resistor (thermistor), light- dependent resistor (LDR), etc. Linear elements obey Ohm’s law whereas non-linear elements do not obey Ohm’s law.

 

 4. The circuit in which current has a complete path to flow is called ______ circuit.

  1. Short
  2. Open
  3. Closed
  4. Open loop

Answer.3. Closed

Explanation

Closed circuit:- A closed circuit is defined as a circuit in which the current has a complete path to flow. When the current path is broken so that current cannot flow, the circuit is called an open circuit.

If there is no break anywhere in the circuit, it is called a closed circuit or complete circuit. Current flows easily in a closed circuit. For example, when a torch is switched on, the circuit becomes closed. Current flows in the circuit and the torch glows.

 

5. How many types of dependent or controlled sources are there?

  1. Two
  2. Four
  3. Three
  4. One

Answer.2. Four

Explanation

  • Dependent source consists of two parts: the controlling part and the controlled part.
  • The controlling part is either an open circuit or a short circuit.
  • The controlled part is either a voltage source or a current source.
  • There are four types of dependent sources that correspond to the four ways of choosing a controlling part and a controlled part.
  • These four dependent sources are called the voltage-controlled voltage source (VCVS), a current-controlled voltage source (CCVS), voltage-controlled current source (VCCS), and current-controlled current source (CCCS).

 

6. If a circuit does not provide complete path for a current flow then it is called as

  1. Open circuit
  2. Closed circuit
  3. Short circuit
  4. False circuit

Answer.1. Open circuit

Explanation:-

Electric current cannot flow if a circuit is open. An open circuit does not provide a complete path for current flow. If the circuit became open, no current would flow. The light bulb would not glow. Free electrons of the conductor would no longer move from one atom to another. An example of an open circuit occurs when a light bulb burns out. The filament (the part that produces light) opens.

The opening in the filament stops current flow from the source of electric energy. This causes the bulb to stop burning, or producing light.

 

7. A circuit having an emf source or any energy source is a/an

  1. Active element
  2. Passive element
  3. Unilateral element
  4. Bilateral element

Answer.1. Active element

Explanation:-

An element which is a source of electrical signal or which is capable of increasing the level of signal energy is termed as active element. Batteries, BJTs, FETs or OP-AMPs are treated as active elements because these can be used for the amplifi cation or generation of signals.

 

8. In a linear circuit, when the ac input is doubled, the ac output becomes

  1. One-fourth
  2. Half
  3. Two times
  4. Four times

Answer.3. Two time

Explanation:-

If the circuit is linear, and you have a single independent voltage source, doubling the voltage source i.e A.C input will double the current and quadruple the power.

 

9. The elements which are not capable of delivering energy by their own are known as

  1. Unilateral elements
  2. Non-linear elements
  3. Passive elements
  4. Active elements

Answer.3. Passive elements

Explanation:- 

A passive element is one which does not generate electricity but either consumes it or stores it. Resistors, inductors and capacitors are simple passive elements. Diodes and transistors are also passive elements.

Passive elements may either be linear or non-linear. Linear elements obey a straight-line law. For example, a linear resistor has a linear voltage vs. current relationship which passes through the origin (V = RI ). A linear inductor has a linear flux  vs. current relationship which passes through the origin ( φ = kI ) and a linear capacitor has a linear charge vs. voltage relationship which passes through the origin (q = CV ). [R, k and C are constants.]

Resistors, inductors and capacitors may be linear or non-linear, while diodes and transistors are always non-linear.

 

10. In _______ system the same relationship exist between current and voltage for current flowing in either direction.

  1. Unilateral
  2. Lumped
  3. Distributed
  4. Bilateral

Answer.4. Bilateral

Explanation

Bilateral circuit: A bilateral circuit is one whose properties or characteristics are the same in either direction, for example, transmission line.

Consider another example of a resistor. When the voltage is applied, current starts to flow. If we change the polarity of the applied voltage, the direction of the current is changed but its magnitude is not affected. Such an element is called a bilateral element.

 

11. Choose the correct statement

Statement 1:- In unilateral circuit characteristics change with the direction of the operation.

Statement 2:- Transistor and Diode are example of unilateral system

  1. Both the statement are correct
  2. Both the statement are incorrect
  3. Only statement 1 is correct
  4. Only statement 2 is correct

Answer.1. Both the statement is correct

Explanation:-

A unilateral circuit is one whose properties or characteristics change with the direction of the operation.

or

If the magnitude of current flowing through a circuit element is affected when the polarity of the applied voltage is changed, the element is termed unilateral element.

For example, in the diode circuit, the characteristic is different in the forward and reverse direction. Thus in a unilateral circuit, the properties or the characteristics are unique in a particular direction of operation.

 

12. The v−i characteristic of an element is shown in Fig. The element is

  1. Non-linear, active, non-bilateral
  2. Linear, active, non-bilateral
  3. Non-linear, passive, non-bilateral
  4. Non-linear, active, bilateral

Answer.2. Linear, active, non-bilateral

Explanation:-

The graph between current and. voltage characteristic is a straight line hence it is linear system.

Since emf source is present to deliver energy therfore it is an active circuit.

From the graph it is clear that when the polarity change the direction of the element is in opposite direction therfore it is a non-bilateral element.

Hence the element is Linear, active, non-bilateral

 

 

13. The v−i characteristic of a resistor is i = 2v2 . The resistor is

  1. Linear, passive, bilateral
  2. Non-linear, active, bilateral
  3. Non-linear, active, unilateral
  4. Non-linear, passive, bilateral

Answer.4. Non-linear, Passive, bilateral

Explanation:-

Given

i = 2v2

The voltage will increase four times as compared to current hence the graph will be Non-Linear.

Resistor can’t generate its own energy therefore it is passive element

If we change the polarity of the applied voltage, the direction of the current is changed but its magnitude is not affected. Such an element is called a bilateral element.

Hence for the above equation the v−i characteristic of a resistor is Non-linear, passive, bilateral.

 

14. Which of the following is true about Lumped Element?

  1. They can’t be sepreated Physically
  2. They can be sepreated Physically
  3. They can’t be used on KCL circuit
  4. They can’t be used on KVL circuit

Answer.2. They can be sepreated Physically

Explanation:-

A lumped element is the element which is separated physically, like resistors, inductors and capacitors. parameters. These elements will be connected together by wires (leads) having practically zero resistance, then the network with number of lumped elements and a set of connecting leads, is called a lumped-parameter network. In such a circuit KVL and KCL holds good.

 

15. Which of the following is not true about Distributed system?

  1. Transmission line is an example of distributed system
  2. The Element can’t be physically seperated
  3. Element can be physically seperated
  4. All of the above

Answer.3. Element can be physically seperated

Explanation:-

A network is said to be distributed if the network elements (R, L, C) cannot be electrically separated and individually isolated as separate eclements. Examples: Transmission lines, winding, of transformers and generators. If the length of transmission line increases or decreases, value of effective (R, L, C) changes and cannot be separated physically.

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