## Electromagnetism Topic Wise MCQs With Answers 2

**Here are some important Electromagnetism topic wise MCQs with answers and explanation for sppu university exams 2020. This contains first 3 topics from sppu syllabus of Electromangnetism Magnetic field of a solenoid, Force on a current carrying conductor, Force determinination.**

Click here for part one of **Electromagnetism mcqs for university exams.**

**“Magnetic Field of a Solenoid”**

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**

Explanation: 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**

Explanation: 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) μn^{2}

c) μNI

d) μN^{2}I^{2}

**Answer: a**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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

**Answer: b**

Explanation: The magnetic field in a solenoid is given by:

B=μnI

Substituting the values in the given values in the equation, I=30A.

10. The magnetic field of the solenoid is 18.84mT, the current is 30A. Calculate the number of turns per unit length if the core is air.

a) 1500 turns/m

b) 1000 turns/m

c) 500 turns /m

d) 2000 turns/m

**Answer: c**

Explanation: The magnetic field in a solenoid is given by:

B=μnI

Substituting the values in the given values in the equation n=500 turns/m

**“Force on a Current Carrying Conductor”.**

1. What is the expression for force in a current carrying conductor?

a) F=Kq1/r^{2}

b) F=Kq2/r^{2}

c) F=Kq1q2/r^{2}

d) F=Kq1q2/r

**Answer: c**

Explanation: 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/r^{2}, 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**

Explanation: 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**

Explanation: 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**

Explanation: From the expression:

F=Kq1q2/r^{2}, the value of K being 9*10^{9}, 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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.

**“Force Determination”.**

1. Which, among the following, is the correct expression for force in a current carrying conductor?

a) F=Bi

b) F=B^{2}il

c) F=Bil

d) F=Bl^{2}

**Answer: c**

Explanation: 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

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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**

Explanation: 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.