Walchand Institute of Technology, Solapur Department of Electronics Engineering Basic Electrical And Electronics Engineering

Walchand Institute of Technology, Solapur

Department of Electronics Engineering

Basic Electrical And Electronics Engineering

1.

-The ____ is responsible for the current to flow in a closed circuit.

a.

Electric charge

b.

Potential difference

c.

Resistance

d.

All of the above

(Ans: b)

7-Resistance of a wire is directly proportional to its

a.

Length

b.

Diameter

c.

Area of cross section

d.

All of the above

(Ans: a)

8-Reciprocal of resistance is called

a.

Resistivity

b.

Conductance

c.

Resonance

d.

None of the above

(Ans: b)

9-A coil consists of 8 turns of copper wire have cross section area of 1mm^2.

The resistance of the coil, when mean length per turn is 0.02μΩm, is

a.

0.96 ohm

b.

0.48 ohm

c.

1.82 ohm

d.

1.44 ohm

(Ans: a)

10-The following is (are) the semiconductor(s)

a.

Silicon

b.

Germanium

c.

Carbon

d.

All of the above

(Ans: d)

11-The resistance of pure metallic conductor _____ with the _______ in

temperature.

a.

increases, increase

b.

increases, decrease

c.

remains same, increase

d.

remains same, decrease

(Ans: a)

12-If three resistance (R1, R2 & R3) are connected in series then

a.

V = IR1 + IR2 + IR3

b.

V = I/R1 + I/R2 + I/R3

c.

I = VR1 + VR2 + VR3

d.

I = V/R1 + V/R2 + V/R3

Where V=Potential difference, I=Current

(Ans: a)

a.

branch currents are additive

b.

conductances are additive

c.

powers are additive

d.

All of the above

(Ans: d)

14- In a DC Circuit, Inductive reactance would be_________

1.

Equal As in AC Circuits

2.

High

3.

Extremely High

4.

Zero

(Ans-4)

15-In DC Circuits, We can improve the Circuit power factor by Capacitors.

1.

True

2.

False

(Ans-2)

16-Kirchhoff’s laws are useful in determining——

1.

Current flowing in a circuit

2.

EMFs and Voltage drops in a circuit

3.

Power in a circuit

4.

All the above

(Ans-4)

17- According to Kirchoff’s voltage law,

a. The algebraic sum of all the e.m.f’s in the circuit is zero

b. Algebraic sum all the voltage drops in the circuit is zero

c. Algebraic sum of e.m.f’s plus algebraic sum of voltage drops is equal to zero

d. All of these

ANSWER: Algebraic sum of e.m.f’s plus algebraic sum of voltage drops is equal

to zero

18- In any network of wires carrying currents, the algebraic sum of all currents

meeting at a point is equal to

a. Sum of all the currents

b. Zero

c. Sum of outgoing current

d. Sum of incoming current

ANSWER: Zero

19- Which among the following is true about ohm’s law?

a. I ∝ V

b. I = V/R

c. V = IR

d. All of these

ANSWER: All of these

20- Specific resistance of a material is

a. Directly proportional to the both area of cross section and length of material

b. Directly proportional to the area of cross section and inversely proportional to the

length of material

c. Inversely proportional to the area of cross section and directly proportional to the

length of material

d. Inversely proportional to the both area of cross section and length of material

Answer Explanation

ANSWER: Directly proportional to the area of cross section and inversely

proportional to the length of material

21- In half wave rectifiers, diode conducts during

a. Only positive half cycle

b. Only negative half cycle

c. Both positive and negative half cycle

d. Neither in positive half cycle nor in negative half cycle

ANSWER: Only positive half cycle

A piece of resistive material has a length of 10 mm, a cross

sectional area of 7 mm

_{and a resistivity of 4700 × 10}

_-m.

What is its resistance?

22-

67

67 m

30.4

30.4 k

Calculate the current I

in the following circuit.

-8A

-2 A

2 A

8 A

Calculate the voltage V

in the following circuit.

24-

-10 V

10 V

12 V

18 V

Determine the open-circuit output voltage of the following

circuit.

5 V

6.82 V

8.18 V

10 V

The effective internal resistance of an ideal current source

is zero.

26-

_True

False

Ans-false

How many meshes are present within the following circuit?

27-

₁

2

3

4

area of the conductor.

length of the conductor.

type of material.

none of these.

29․ The resistance of a conductor of diameter d and length l is R Ω. If the diameter

of the conductor is halved and its length is doubled, the resistance will be

R Ω

2R Ω

4R Ω

8R Ω

30․ The unit of resistivity is

Ω.

Ω - metre.

Ω / metre.

Ω / m².

31․ If P is the power of a star connected system then what will be power of an

equivalent delta connected system?

P

3P

P/3

None of the above

32․ Internal resistance of ideal voltage source is

zero

infinite

finite

100 ohms

33- A 100 watt, 250 V bulb will have more resistance than 60 watt, 250 V bulb.

a) True

b) False

Ans: (b)

34.If the network does not contain any energy source is called as

a)Bilateral network b)Unilateral Network c)active network d)passive network

35)A 25W,220v bulb and 100W,220v bulb are joined in parallel and connected in

220v supply which bulb will glow more brightly?

a)25W bulb b)100W bulb c)both will glow with same brightness d)neither

bulb will glow

36) Star connection is also known as__________

b) Mesh connection

d) Neither Y-connection nor mesh connection Answer: a

Explanation: The star connection is also known as the Y-connection because its formation is like the letter Y.

38) Rab is the resistance between the terminals A and B, Rbc between B and C and Rca between C and A. These 3 resistors are connected in delta connection. After transforming to star, the resistance at B will be?

a) Rac/(Rab+Rbc+Rca) b) Rab/(Rab+Rbc+Rca) c) Rbc*Rab/(Rab+Rbc+Rca) d) Rab/(Rab+Rbc+Rca) Answer: c

39)If a 6 ohm, 2ohm and 4ohm resistor is connected in delta, find the equivalent star connection.

a) 1ohm, 2ohm, 3ohm b) 2ohm, 4ohm, 7ohm c) 5ohm, 4ohm, 2ohm d) 1ohm, 2ohm, 2/3ohm Answer: d

Explanation: Using the delta to star conversion formula: R1=2*6/(2+6+4)

R2=2*4/(2+6+4) R3=4*6/(2+6+4).

40) If a 4ohm, 3ohm and 2ohm resistor is connected in delta, find the equivalent star connection.

a) 8/9ohm, 4/3ohm, 2/3ohm b) 8/9ohm, 4/3ohm, 7/3ohm c) 7/9ohm, 4/3ohm, 2/3ohm d) 8/9ohm, 5/3ohm, 2/3ohm Answer: a

Explanation: Using the delta-star conversion formula: R1=4*3/(2+3+4)

R2=2*3/(2+3+4) R3=2*4/(2+3+4).

41)Find the current in the circuit.

b) 0.65A c) 0.67A d) 0.87A Answer: a

Explanation: The 3 5 ohm resistors are connected in delta. Changing it to star: R1=R2=R3 = 1.67 ohm.

One of the 1.67 ohm resistors are connected in series with the 2 ohm resistor and another 1.67 ohm resistor is connected in series to the 3 ohm resistor.

The resulting network has a 1.67 ohm resistor connected in series with the parallel connection of the 3.67 and 4.67 resistors.

The equivalent resistance is 3.725A. I=2/3.725 = 0.54A.

42) It is preferable to connect bulbs in series or in parallel? a) Series

b) Parallel

c) Both series and parallel d) Neither series nor parallel Answer: b

Explanation: Bulbs are connected in parallel so that even if one of the bulbs blow out, the others continue to get a current supply.

43) Calculate the total resistance between the points A and B.

a) 7 ohm b) 0 ohm c) 7.67 ohm d) 0.48 ohm Answer: c

Explanation: 1 ohm in parallel with 2 ohm give 2/3 ohm equivalent which is in series with 4 ohm and 3 ohm so total resistance between A and B = 4 + 2/3 + 3 = 23/3 = 7.67 ohm.

44). Calculate the equivalent resistance between A and B. a) 60 ohm b) 15 ohm c) 12 ohm d) 48 ohm Answer: c

Explanation: 5 ohm and 15 ohm are connected in series to give 20 ohm.10ohm and 20 ohm are connected in series to give 30 ohm. Now both equivalent resistances (20ohm and 30 ohm) are in parallel to give equivalent resistance 20*30/(20+30) = 12 ohm.

45) Calculate the resistance between A and B.

a) 3.56 ohm b) 7 ohm c) 14.26 ohm d) 29.69 ohm Answer: a

Explanation: The 1 ohm, 2 ohm and 3 ohm resistors are connected in parallel. Its equivalent resistance is in series with the 4 ohm resistor and the parallel connection of the 5 ohm and 6 ohm resistor. The equivalent resistance of this combination is 80/11 ohm. This is in parallel with 7 ohm to give equivalent resistance between A and B is 3.56 ohm.

46) Batteries are generally connected in______ a) Series

c) Either series or parallel d) Neither series nor parallel Answer: a

Explanation: Batteries are generally connected in series so that we can obtain the desired voltage since voltages add up once they are connected in series.

47) In a _________ circuit, the total resistance is greater than the largest resistance in the circuit.

a) Series b) Parallel

c) Either series or parallel d) Neither series nor parallel Answer: a

Explanation: In series circuits, the total resistance is the sum of all the resistance in the circuit, hence the total is greater than the largest resistance.

48) In a ____________ circuit, the total resistance is smaller than the smallest resistance in the circuit.

a) Series b) Parallel

c) Either series or parallel d) Neither series nor parallel Answer: b

Explanation: in a parallel circuit, the equivalent resistance=1/sum of the reciprocals of all the resistances in the circuit. Hence it is smaller than the smallest resistance in the circuit.

49) Which is the most cost efficient connection? a) Series

b) Parallel

c) Either series or parallel d) Neither series nor parallel Answer: a

Explanation: The advantage of series-connections is that they share the supply voltage, hence cheap low voltage appliances may be used.

a) 2 ohm b) 4 ohm c) 6 ohm d) 8 ohm Answer: b

Explanation: R=((2+3)||5)+1.5)||4. The 2 and the 3 ohm resistor are in series. The equivalent of these two resistors is in parallel with the 5 ohm resistor. The equivalent of these three resistances is in series with the 1.5 ohm resistor. Finally, the

equivalent of these resistances is in parallel with the 4 ohm resistor. 51) Calculate the equivalent resistance between A and B.

a) 6.67 ohm b) 46.67 ohm c) 26.67 ohm d) 10.67 ohm Answer: a

Explanation: R=20||20||20=6.67 ohm. The three 20 ohm resistors are in parallel and re-sistance is measured across this terminal.