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# Multiple choice question for engineering

## Set 1

1. Find the value of I1, I2 and I3. a) -0.188A, 1.5A, -1.19A
b) -1.5A, -0.188A, 1.19A
c) 1.5A, -0.188A, -1.19A
d) 1.19A, 0.188A, 1.5A

Answer: c [Reason:] Using the matrix method: Matrix(3,-2,0) (I1)=(5) (-2,9,-4) (I2)=(0) (0,-4,9) (I3)=(-10) Solving this matrix equation, we get I1=1.5A, I2=-0.188A and I3=-1.19A.

2. Find the value of V, if the value of I3= 0A. a) 7.5V
b) 6.5V
c) 5.5V
d) 4.5V

Answer: a [Reason:] Using the matrix method: Matrix(3,-2,0) (I1)=(5) (-2,9,-4) (I2)=(0) (0,-4,9) (0)=(-V) Solving the matrix, we get V=7.5V.

3. Find the value of R if the power in the circuit is 1000W. a) 10 ohm
b) 9 ohm
c) 8 ohm
d) 7 ohm

Answer: c [Reason:] To find the value of I: VI=P =>100I=1000 => I=10A. Voltage across the 2 ohm resistor= 20V. Voltage across the R resistor= 100-20= 80V. R=V/I => R=80/10= 8A.

4. Find the current in the 4 ohm resistor. a) 5A
b) 0A
c) 2.2A
d) 20A

Answer: a [Reason:] The 4 ohm resistor gets shorted since current always prefers the low resistance path. All the current flows to the branch which is connected in parallel to the 4 ohm branch, hence no current flows in the 4 ohm resistance.

5. Nodal analysis is generally used to determine______
a) Voltage
b) Current
c) Resistance
d) Power

Answer: a [Reason:] Nodal analysis uses Kirchhoff’s Current Law to find all the node voltages. Hence it is a method used to determine voltage.

6. Mesh analysis is generally used to determine_________
a) Voltage
b) Current
c) Resistance
d) Power

Answer: b [Reason:] Mesh analysis uses Kirchhoff’s Voltage Law to find all the mesh currents. Hence it is a method used to determine current.

7. What is the current in the circuit? a) 0A
b) 15A
c) 5A
d) 10A

Answer: a [Reason:] If we move in the clockwise direction, we get the total voltage to be equal to: -10-20+30= 0V. Since I=V/R= 0/4=0, I=0A.

8. Does the 15A source have any effect on the circuit? a) Yes
b) No
c) Cannot be determined
d) Yes, only when the 10V source is removed

Answer: b [Reason:] The 15A current source has a lower resistance path associated with it and hence it keeps moving in that particular loop. It does not leave that loop and enter the circuit, hence the circuit is not affected by it.

9. KVL is associated with____________
a) Mesh analysis
b) Nodal analysis
c) Both mesh and nodal
d) Neither mesh nor nodal

Answer: a [Reason:] KVL employs mesh analysis to find the different mesh currents by finding the IR products in each mesh.

10. KCL is associated with_________
a) Mesh analysis
b) Nodal analysis
c) Both mesh and nodal
d) Neither mesh nor nodal

Answer: b [Reason:] KCL employs nodal analysis to find the different node voltages by finding the value if current in each branch.

## Set 2

1. Calculate the value of V1 and V2. a) 4V, 6V
b) 5V, 6V
c) 6V, 7V
d) 7V, 8V

Answer: a [Reason:] Using KVL, 12-V1-8=0. V1= 4V. 8-V2-2=0. V2=6V.

2. KCL deals with the conservation of?
a) Mass
b) Momentum
c) Charge
d) Energy

Answer: d [Reason:] KVL states that the sum of the potential energy and taken with the right sign is equal to zero, hence it is the conservation of energy since energy doesn’t enter of leave the system.

3. Calculate the voltage across the 10 ohm resistor. a) 12V
b) 4V
c) 10V
d) 0V

Answer: b [Reason:] Using voltage divider rule, V=10*12/30=4V.

4. Find the value of the currents I1 and I2. a) 0.3, 0.1
b) -0.1, -0.3
c) -0.3, -0.1
d) 0.1, 0.3

Answer: c [Reason:] Using KVL, the matrix to find the loop currents are: MATRIX( 0 -100)(I1)=(10) MATRIX( -100 200)(I2) (10) I1= -0.3, I2=-0.1.

5. The sum of the voltages over any closed loop is equal to __________
a) 0V
b) Infinity
c) 1V
d) 2V

Answer: a [Reason:] According to KVL, the sum of the voltage over any closed loop is equal to 0.

6. What is the basic law that has to be followed in order to analyze ant circuit?
a) Newton’s laws
c) Ampere’s laws
d) Kirchhoff’s law

Answer: d [Reason:] Kirchhoff’s laws, namely Kirchhoff’s Current Law and Kirchhoff’s Voltage law are the basic laws in order to analyze a circuit.

7. Every____________ is a ____________ but every __________ is not a __________
a) Mesh, loop, loop, mesh
b) Loop, mesh, mesh, loop
c) Loop, mesh, loop, mesh
d) Mesh, loop, mesh, loop

Answer: a [Reason:] According to Kirchhoff’s Voltage Law, Every mesh is a loop but every loop is not a mesh.

8. What is the voltage across the 5 ohm resistor? a) 2.32V
b) 5.21V
c) 6.67V
d) 8.96V

Answer: b [Reason:] In loop 1: i1(2+3+4)-i2*4-9-4+5=0 => 9i1-4i2=8. In loop 2 i2(4+1+5)-4i1-5=0 =>-4i1+10i2=5. Solving these equations simultaneously i2=1.041A and i1=1.352A V=i2*5= 5.21V.

9. Calculate VAB. a) 3.5V
b) 12V
c) 9.5V
d) 6.5V

Answer: a [Reason:] For branch A: VAC=15*20/(25+15)=7.5V For branch B: VBC= 10*20/(10+40)=4V Applying KVL to loop ABC: VAB+VBC+VCA=0 VAB=3.5V.

10. KVL is applied in ____________
a) Mesh analysis
b) Nodal analysis
c) Both mesh and nodal
d) Neither mesh nor nodal

Answer: a [Reason:] Mesh analysis helps us to utilize the different voltages in the circuit as well as the IR products in the circuit which is nothing but KVL.

## Set 3

1. Leakage in capacitors is primarily caused by _________
a) Transistors
b) Resistors
c) Inductors
d) DC motors

Answer: a [Reason:] Leakage is primarily caused due to electronic devices, such as transistors, connected to the capacitors. Transistors conduct a small amount of current even when they are turned off, hence they are responsible for leakage current.

2. What is the conduction current when a capacitor is fully charged?
a) Infinity
b) Zero
c) 100A
d) 1000A

Answer: b [Reason:] When a capacitor is fully charged, there is no conduction of electrons from one plate of the capacitor to another, hence there is no conduction current and conduction current is equal to zero.

3. The flow of electrons in dielectric is due to _________
a) Conduction
b) Potential difference
c) Breakdown
d) Resistance

Answer: c [Reason:] There is, under normal circumstance, no flow of electrons in a dielectric since a dielectric is basically an insulator. Hence, there is flow of electrons in a dielectric only at breakdown voltage.

4. The flow of electrons which does not pass through the battery is known as ________
a) Conduction current
b) Leakage current
c) Either conduction or leakage current
d) Neither conduction nor leakage current

Answer: a [Reason:] Conduction current is the flow of electrons from the positive plate of the capacitor to the negative plate of the capacitor, not through the battery. Hence the type of current which flows without passing through the battery is conduction current.

5. The free electrons in practical dielectrics is due to _________
a) There are no free electrons
b) Conductors
c) Impurities
d) Both conductors and impurities

Answer: c [Reason:] Ideally, dielectrics are insulators and do not contain any free electrons. But no dielectric is a perfect dielectric, hence the free electrons are due to impurities present in each dielectric.

6. The current in conductors connecting the voltage source to the plates of a capacitor is ______
a) Conduction current
b) Leakage current
c) Charging current
d) Zero

Answer: c [Reason:] The current in conductors connecting the voltage source to the plates of a capacitor is the charging current and not the conduction or leakage current.

7. What is the type of current where the electrons actually move?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: b [Reason:] Conduction current is the current caused by the actual flow of electrons and displacement current is the current where no charge carriers are involved.

8. What is the type of current caused due to variations in the field?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: a [Reason:] Displacement current is the current where no charge carriers are involved. It is caused due to variations in the electric field.

9. Under normal conditions capacitors have _________
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: a [Reason:] Under normal conditions capacitors contain an insulating material called dielectric sandwiched between the plates of the capacitor. Since insulators can carry only an electric field but not moving carriers, therefore normally a capacitor has displacement current and not conduction current.

10. If a large amount of voltage is applied to a capacitor, what is the current that flows through it?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: b [Reason:] When a large amount of voltage is applied between the plates of a capacitor, the dielectric between the plates does not behave as an insulator anymore and starts conducting and conduction currents flow through it.

## Set 4

1. What is the magnetic field outside a solenoid?
a) Infinity
b) Half the value of the field inside
c) Double the value of the field inside
d) Zero

Answer: d [Reason:] There are no magnetic lines of force outside a solenoid, hence the magnetic field outside a solenoid is zero.

2. Which, among the following qualities, is not affected by the magnetic field?
a) Moving charge
b) Change in magnetic flux
c) Current flowing in conductor
d) Stationary charge

Answer: d [Reason:] A stationary charge is not affected by a magnetic field because stationary charges do not have any velocity. Magnetic field cannot occur in a particle having zero velocity.

3. When a charged particle moves at right angles to the magnetic field, the variable quantity is?
a) Momentum
b) Speed
c) Energy
d) Moment of inertia

Answer: a [Reason:] When a charged particle moves perpendicular to the field, its speed remains the same whereas its velocity keeps on changing. Momentum is the product of the mass of the particle and the velocity if the particle, hence since velocity varies, momentum also varies.

4. If the flow of electric current is parallel to the magnetic field, the force will be ______
a) Zero
b) Infinity
c) Maximum
d) Half the original value

Answer: a [Reason:] Force is a cross product. A cross product involves the sine of the angle between them. If two quantities are parallel to each other, the angle between them is zero. Sin(0) is zero, hence force is zero.

5. The ratio of magnetic force to electric force on a charged particle getting undeflected in a field is?
a) 1
b) 0
c) 2
d) 4

Answer: a [Reason:] When a charged particle is undeflected in a field, the magnitude of the magnetic force and electric force acting on the particle is the same, hence the ratio is 1.

6. What is the strength of magnetic field known as ________
a) Flux
b) Density
c) Magnetic strength
d) Magnetic flux density

Answer: d [Reason:] Strength of magnetic filed is also known as magnetic flux density. It is the amount of magnetic flux lines crossing through unit area.

7. Weakest force in nature is?
a) Electric force
b) Gravitational force
c) Weak force
d) Magnetic force

Answer: a [Reason:] Gravitational force is the weakest force in nature as it does not bind anything strongly with its help.

8. How can a magnetic field be produced?
a) Using a permanent magnet
b) Electric current
c) Using a temporary magnet
d) Using a permanent magnet or electric current

Answer: d [Reason:] An electric filed as well as a permanent magnet produces a magnetic field whereas a temporary magnets fails to do so.

9. Can we see magnetic flux lines?
a) Yes
b) No
c) Depends on the strength of the field
d) Only when field strength is very large

Answer: b [Reason:] No, we cannot see magnetic flux lines as the “lines of magnetic flux” is purely an imaginary concept to understand the magnetic field clearly.

10. Magnetic Field lines move from _______
a) North to south
b) South to north
c) West to east
d) East to west

Answer: a [Reason:] Magnetic field lines originate at the north pole and terminate at the south pole of the magnet.

## Set 5

1. The magnetic field strength of a solenoid can be increased by inserting which of the following materials as the core?
a) Copper
b) Silver
c) Iron
d) Aluminium

Answer: c [Reason:] The Magnetic field of a solenoid increases when we insert a iron core because, iron is a ferromagnetic material and ferromagnetic materials help in increasing the magnetic property.

2. If a coil is wound around a steel core and electric current is passed through the coil, the steel core acts as a?
a) Electromagnet
b) Permanent magnet
c) Neither electromagnet nor permanent magnet
d) Either electromagnet or permanent magnet

Answer: b [Reason:] When a coin is wound around a steel core, the steel core behaves as a permanent magnet because it is a ferromagnetic material and once it becomes magnetic it does not lose its magnetic property.

3. What is the formula for magnetic field due to a solenoid?
a) μnI
b) μn2
c) μNI
d) μN2I2

Answer: a [Reason:] The magnetic field due to a solenoid is: B= μnI, where μ is the permeability, n is the number of turns per unit length and I is the current in the solenoid.

4. What happens to the magnetic field in the solenoid when the number of turns increases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero

Answer: a [Reason:] The magnetic field of a solenoid is directly proportional to the number of turns in it. Hence as the number of turns increases, the magnetic field also increases.

5. What happens to the magnetic field in the solenoid when the current increases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero

Answer: a [Reason:] The magnetic field of a solenoid is directly proportional to the current in it. Hence as the current increases, the magnetic field also increases.

6. What happens to the magnetic field in the solenoid when the length of the solenoid increases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero

Answer: b [Reason:] The magnetic field of a solenoid is inversely proportional to the length. Hence as the length increases, the magnetic field decreases.

7. What is the magnetic field outside a solenoid?
a) Infinity
b) Half the value of the field inside
c) Double the value of the field inside
d) Zero

Answer: d [Reason:] There are no magnetic lines of force outside a solenoid, hence the magnetic field outside a solenoid is zero.

8. The current in a solenoid is 30A, the number of turns per unit length is 500 turns per metre. Calculate the magnetic field if the core is air.
a) 18.84T
b) 18.84mT
c) 1.84T
d) 1.84mT

Answer: b [Reason:] The magnetic field in a solenoid is given by: B=μnI Substituting the values in the given values in the equation, B=18.84mT.

9. The magnetic field of the solenoid is 18.84mT, the number of turns per unit length is 500 turns per metre. Calculate the current if the core is air.
a) 300A
b) 30A
c) 3A
d) 300mA