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# Multiple choice question for engineering

## Set 1

1. What is the expression for force in a current carrying conductor?
a) F=Kq1/r2
b) F=Kq2/r2
c) F=Kq1q2/r2
d) F=Kq1q2/r

Answer: c [Reason:] The force in a current carrying conductor is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them. Hence F=Kq1q2/r2, where K is the constant of proportionality.

2. Force in a conductor is__________ to the product of the charges.
a) Directly proportional
b) Inversely proportional
c) Not related
d) Cannot be determined

Answer: a [Reason:] The force in a current carrying conductor is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.

3. Force in a conductor is __________ to the square of the distance between the charges.
a) Directly proportional
b) Inversely proportional
c) Not related
d) Cannot be determined

Answer: b [Reason:] The force in a current carrying conductor is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.

4. Calculate the force between two charges having magnitude 3nC and 2nC separated by a distance of 2micro m.
a) 13.5N
b) 13.5kN
c) 1.35N
d) 1.35kN

Answer: b [Reason:] From the expression: F=Kq1q2/r2, the value of K being 9*109, we get F=13.5kN.

5. 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.

6. 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.

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. According to Flemming’s left hand rule, the thumb denotes?
a) Direction of magnetic field
b) Direction of current
c) Direction of force
d) Direction of force as well as current

Answer: c [Reason:] According to Flemming’s left hand rule, the index finger denotes the direction of magnetic field, the thumb denoted the direction of force and the middle finger denoted the direction of current.

9. The relation between the direction of force and the direction of magnetic field is __________
a) Same direction
b) Opposite direction
c) Perpendicular
d) Unrelated

Answer: c [Reason:] When a conductor carries a certain value of current, the force developed in the conductor, the current in the conductor and the magnetic field in the conductor are mutually perpendicular to each other.

10. The relation between the direction of current and the direction of force is ________
a) Same direction
b) Opposite direction
c) Perpendicular
d) Unrelated

Answer: c [Reason:] When a conductor carries a certain value of current, the force developed in the conductor, the current in the conductor and the magnetic field in the conductor are mutually perpendicular to each other.

## Set 2

1. Which, among the following, is the correct expression for force in a current carrying conductor?
a) F=Bi
b) F=B2il
c) F=Bil
d) F=Bl2

Answer: c [Reason:] The correct expression for force in a current carrying conductor in a magnetic field is F=Bil, where B is the magnetic field, i is the current in the conductor and l is the length of the conductor.

2. When the current in the current carrying conductor increases, what happens to the force in the conductor which is at right angles to the magnetic field?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: a [Reason:] The force at right angles to the magnetic field of a current carrying conductor increases when the current increases because it is directly proportional to the force.

3. When the length of the conductor in the current carrying conductor increases, what happens to the force in the conductor which is at right angles to the magnetic field?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: a [Reason:] The force at right angles to the magnetic field of a current carrying conductor increases when the length of the conductor increases because it is directly proportional to the force.

4. When the magnetic field intensity in the current carrying conductor increases, what happens to the force in the conductor which is at right angles to the magnetic field?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: a [Reason:] The force at right angles to the magnetic field of a current carrying conductor increases when the magnetic field intensity increases because it is directly proportional to the force.

5. The unit for force in a current carrying conductor is _________
a) Newton
b) Tesla
c) Weber/metre
d) Ampere

Answer: a [Reason:] The unit foe force in a current carrying conductor is newton because it is a force and the unit of force is newton.

6. 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.

7. 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.

8. If the intensity of magnetic field is 100T, the length of the conductor is 3m and the current in the conductor is 10A, calculate the magnitude of force perpendicular to the electric field.
a) 300N
b) 30N
c) 30kN
d) 3kN

Answer: d [Reason:] The formula for calculating the value of the force which is perpendicular to the electric field is: F=Bil Substituting the values from the question, we get F=3kN.

9. 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.

10. The relation between the direction of force and the direction of magnetic field is _________
a) Same direction
b) Opposite direction
c) Perpendicular
d) Unrelated

Answer: c [Reason:] When a conductor carries a certain value of current, the force developed in the conductor, the current in the conductor and the magnetic field in the conductor are mutually perpendicular to each other.

## Set 3

1. If the resonant frequency in a series RLC circuit is 50kHz along with a bandwidth of 1kHz, find the quality factor.
a) 5
b) 50
c) 100
d) 500

Answer: b [Reason:] We know that Quality factor is equal to the resonant frequency divided by the bandwidth. Substituting the values from the given question, we get Q=50.

2. What is the SI unit for quality factor?
a) Hz
b) kHz
c) MHz
d) No unit

Answer: d [Reason:] We know that Quality factor is equal to the resonant frequency divided by the bandwidth. It is one frequency divided by another hence it has no unit.

3. What happens to the quality factor when the bandwidth increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: b [Reason:] We know that Quality factor is equal to the resonant frequency divided by the bandwidth. Hence as the bandwidth increases, quality factor decreases.

4. What happens to the quality factor when resonant frequency increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: a [Reason:] We know that Quality factor is equal to the resonant frequency divided by the bandwidth. Hence as the resonant frequency increases, quality factor also increases.

5. Resonant frequency is when ___________
a) XL=XC
b) XL>XC
c) XL<XC
d) Cannot be determined

Answer: a [Reason:] The frequency of a system is said to be resonating when the value of the capacitive reactance and the inductive reactance is the same.

6. What is the frequency in resonance condition?
a) Minimum
b) Maximum
c) Cannot be determined
d) Zero

Answer: b [Reason:] At resonance condition, the frequency is maximum since the inductive reactance is equal to the capacitive reactance and the voltage and current are in phase.

7. The current leads the supply voltage in a series RLC circuit has its frequency _________ the resonant frequency.
a) Above
b) Below
c) Equal to
d) Cannot be determined

Answer: b [Reason:] The current leads the voltage in a series RLC circuit when the supply voltage is less than the resonant voltage.

8. What is the power factor of a series RLC circuit under resonance condition?
a) 0
b) 1
c) Infinity
d) 100

Answer: 1 [Reason:] The power factor for a series RLC circuit in resonance condition is always 1 because the current is in phase with the voltage under resonance condition.

9. In resonance condition, current ________ voltage.
b) Lags
c) Is in phase with
d) Is greater than

Answer: c [Reason:] In resonance condition of a series RLC circuit, the current is always in phase with the voltage because the reactance is neither capacitive nor inductive.

10. What is the correct formula for quality factor?
a) Q=BW*fr
b) Q=BW/fr
c) Q=fr/BW
d) Q=fr2

Answer: c [Reason:] The correct formula for quality factor is Q=fr/BW, where fr is the resonant frequency, BW is the bandwidth frequency and Q is the quality factor.

## Set 4

1. The total voltage drop across a series of capacitors is __________
a) The voltage drop across any one of the capacitors
b) The sum of the voltage drop across each of the capacitors
c) The product of the voltage drop across each of the capacitors
d) Zero

Answer: b [Reason:] The total voltage drop is equal to the sum of the voltage drop across each off the capacitors because when capacitors are connected in series, the voltage drops across each capacitor.

2. Capacitors C1, C2 and C3 have voltage drops 2V, 3V and 5V respectively. Calculate the total voltage in the circuit.
a) 10V
b) 2V
c) 5V
d) 0V

Answer: a [Reason:] When capacitors are connected in series: Vtotal=V12+V2+V3= 2+3+5=10V.

3. What is the voltage across the 2F capacitor? a) 242V
b) 2V
c) 220V
d) 121V

Answer: d [Reason:] The equivalent capacitance is equal to: 1/C=1/2+1/4+1/6, therefore, C=1.1F. Q=C*V= 220*1.1= 242C. V across 2F capacitor = Q/C= 242/2= 121V.

4. What is the voltage across the 4F capacitor? a) 242V
b) 60.5V
c) 22.5V
d) 12.5V

Answer: b [Reason:] The equivalent capacitance is equal to: 1/C=1/2+1/4+1/6, therefore, C=1.1F. Q=C*V= 220*1.1= 242C. V across 4F capacitor = Q/C= 242/4= 60.5V.

5. Calculate the voltage across the 6F capacitor. a) 242V
b) 60.5V
c) 40.33V
d) 12.5V

Answer: c [Reason:] The equivalent capacitance is equal to: 1/C=1/2+1/4+1/6, therefore, C=1.1F. Q=C*V= 220*1.1= 242C. V across 6F capacitor = Q/C= 242/6= 40.33V.

6. When capacitors are connected in series, which of the following rules are applied?
a) Voltage divider
b) Current divider
c) Both voltage divider and current divider
d) Neither voltage divider nor current divider

Answer: a [Reason:] Voltage divider is the rule applied when capacitors are connected in series because when capacitors are connected in series, the voltage is different across each capacitor.

7. A capacitor does not allow sudden changes in _________
a) Current
b) Voltage
c) Resistance
d) Inductance

Answer: b [Reason:] Capacitor does not allow sudden changes in voltage because these changes occur in zero time which results in the current being infinity, which is not possible.

8. Which of the following expressions is correct with respect to the voltage across capacitors in series?
a) V1/V2=C2/C1
b) V2/V1=C2/C1
c) V1*V2=C1*C2
d) V1/C1=V2/C2

Answer: a [Reason:] When capacitors are connected in series, the charge across each capacitor remains the same whereas the voltage across each varies. When two capacitors are connected in series: Q=V1C1; Q=V2C2. Thus: V1/V2=C2/C1.

9. Two 4F capacitors are connected in series, calculate the voltage across each if the total voltage is 20V.
a) 10V
b) 5V
c) 20V
d) 0V

Answer: a [Reason:] The two capacitors have the same capacitance, hence the voltage gets divides equally. V across each=Total voltage/2= 20/2= 10V.

10. Two capacitors having voltage 2F and 4F are connected in series. This combination is connected to a 100V supply, calculate the voltage across the 2F capacitor.
a) 66.67V
b) 33.33V
c) 100V
d) 0V

Answer: b [Reason:] Using voltage divider rule: V across 2F= 100*2/(2+4)= 33.33V.

## Set 5

1. Which, among the following, is the correct expression for alternating emf generated?
a) e=2Blusin(theta)
b) e=2B2lusin(theta)
c) e=Blusin(theta)
d) e=4Blusin(theta)

Answer: a [Reason:] The correct expression foe alternating emf generated is e=2Blusin(theta). Where, B stands for magnetic field density, l is the length of each of the parallel sides u is the velocity with which the conductor is moved and theta is the angle between the velocity and the length.

2. What should theta be in order to get maximum emf?
a) 0
b) 90
c) 180
d) 45

Answer: b [Reason:] The value of theta should be 90 in order to get maximum emf because e=2Blusin(theta) and sin is maximum when theta is 90.

3. Calculate the maximum emf when the velocity is 10m/s, the length is 3m and the magnetic field density is 5T.
a) 150V
b) 100V
c) 300V
d) 0V

Answer: c [Reason:] We know that: e=2Blusin(theta) Substituting the values from the given question, we get e=300V.

4. When a coil is rotated in a magnetic field, the emf induced in it?
a) Is maximum
b) Is minimum
c) Continuously varies
d) Remains constant

Answer: c [Reason:] When a coil is rotated in a magnetic field the emf continuously varies as the cross sectional area varies due to which the number of flux lines crossing it varies, which causes the emf to vary.

5. An E.M.F. can be induced by ___________
a) Change in magnetic field
b) Change in the area of cross section
c) Change in angle between magnetic field and area
d) Change in magnetic field, area and angle

Answer: d [Reason:] This is the dot product of magnetic field vector and area vector. emf=BAcos(theta), hence if either of the three, that is, magnetic field, area or angle changes, thee emf will change.

6. What is emf?
a) Force
b) Voltage
c) Current
d) Flux

Answer: b [Reason:] Electromotive force is not actually a force. It is basically a voltage. It is the voltage developed by any source of electrical energy.

7. What is the consequence of motor effect?
a) Current
b) Voltage
c) Electromagnetic induction
d) EMF

Answer: c [Reason:] Motor effect is when a current carrying conductor in a magnetic field experiences a force, hence its consequence is electromagnetic induction.

8. The total number of magnetic field lines passing through an area is termed as?
a) Voltage
b) EMF
c) Magnetic flux
d) Magnetic flux density

Answer: b [Reason:] The number of magnetic flux lines per unit area is the magnetic flux, because flux is the number of field lines per unit area.

9. In an A.C. generator, increase in number of turns in the coil _________
a) Increases emf
b) Decreases emf
c) Makes the emf zero
d) Maintains the emf at a constant value