Magnetism MCQ Quiz - Objective Question with Answer for Magnetism - Download Free PDF

The correct answer is the Direction of the magnetic field.

Key Points

Fleming's Right-Hand Rule:

• Thumb: It is along the direction of motion of the conductor.
• Middle Finger: Indicates the direction of the induced current.
• Index Finger(forefinger):  Indicates the direction of the magnetic field.

Image: Fleming's Right-Hand Rule

Fleming's Left-Hand Rule:

• Thumb: It points towards the direction of motion (force)
• Middle Finger: It represents the direction of the induced current
• Index Finger:  It represents the direction of the magnetic field.   

Important Points 

• Fleming's left-hand rule is used for electric motors.
• Fleming's Right-Hand Rule is used for electric generators

The correct answer is Electric heater.

Key Points

• An electric heater works by converting electrical energy into heat energy using resistive heating elements.
• It does not rely on the interaction of a current-carrying conductor with a magnetic field to generate heat.
• Electric motors use current-carrying conductors in magnetic fields to produce mechanical motion.
• Electric fans use electric motors, which in turn use current-carrying conductors in magnetic fields to operate.
• Electric generators convert mechanical energy into electrical energy through the use of current-carrying conductors in magnetic fields.

Additional Information

• Electric Motor
  • It operates on the principle of the Lorentz force, where a current-carrying conductor in a magnetic field experiences a force.
  • Used in various applications including fans, pumps, and household appliances.
• Electric Generator
  • Works on the principle of electromagnetic induction, where a conductor moving in a magnetic field induces an electromotive force (EMF).
  • Commonly used to provide power in places without access to the electrical grid.
• Electric Fan
  • Uses an electric motor to convert electrical energy into mechanical energy, causing the blades to rotate and move air.
  • Electric fans are widely used for cooling and ventilation purposes.

The correct answer is Iron.

Key Points

• A magnetic compass is a navigational instrument used to determine directions.
• The primary material used in making the needle of a magnetic compass is iron or steel, as these materials can be magnetized.
• When magnetized, iron aligns itself with the Earth's magnetic field, allowing the compass needle to point towards the magnetic north.
• Steel is often preferred for the needle because it retains magnetism for a longer time than pure iron.
• The magnetic property of iron makes it an ideal material for creating functional and reliable compass needles.
• The use of magnetic materials ensures the compass remains accurate and durable for navigation purposes.
• Magnetic compasses have been widely used for centuries in fields like navigation, exploration, and military operations.

Additional Information

• Copper
  • Copper is a non-magnetic material and cannot be used for making compass needles.
  • It is widely used in electrical wiring, electronics, and plumbing due to its high conductivity and resistance to corrosion.
• Wood
  • Wood is an organic material and is not magnetic in nature.
  • It is primarily used in construction, furniture, and as a raw material for products like paper and textiles.
  • Due to its lack of magnetic properties, it cannot be used in manufacturing magnetic compass needles.
• Steel
  • Steel, an alloy of iron and carbon, is a magnetic material and is often used to make compass needles.
  • It has the advantage of retaining magnetism longer than pure iron, making it a good alternative for compass manufacturing.
  • Its durability and resistance to corrosion add to its advantages in making reliable navigation tools.

The correct answer is Polarity.

Key Points

• Polarity refers to the property of magnets where they have two distinct poles: north (N) and south (S). Like poles repel, and unlike poles attract.
• This property arises due to the alignment of magnetic domains within the material, which creates a magnetic field with directional characteristics.
• The force of attraction or repulsion between magnets is governed by the interaction of their poles and the magnetic field they produce.
• Polarity is a fundamental aspect of magnetism, enabling magnets to exhibit behaviors such as attraction to ferromagnetic materials and alignment with Earth's magnetic field.

Additional Information

• Magnetic Field:
  • A magnetic field is the region around a magnet where its magnetic force can be detected.
  • The strength of the magnetic field is highest near the poles of the magnet.
  • Field lines emerge from the north pole and enter the south pole, forming a closed loop.
• Magnetic Domains:
  • Magnetic domains are regions within a material where the magnetic moments of atoms are aligned in the same direction.
  • In unmagnetized materials, these domains are randomly oriented, whereas in magnetized materials, they are aligned.
• Ferromagnetic Materials:
  • Materials like iron, cobalt, and nickel are strongly attracted to magnets due to their high magnetic permeability.
  • These materials can be magnetized to become permanent magnets.
• Earth’s Magnetic Field:
  • The Earth itself acts as a giant magnet with a magnetic field, which is why magnets align with its poles when freely suspended.
  • This is the principle behind the working of a magnetic compass.

The correct answer is Statement I and II are correct.

Key Points

• Statement I: Correct, A magnetic compass is a navigation instrument used to find directions by aligning itself with Earth's magnetic field.
• Statement II: Correct, A magnet always has two poles (north and south) and cannot exist with just one pole; this is a fundamental property of magnets.
• Statement III: Correct, similar poles of a magnet repel each other (north-north or south-south).
• Statement IV: Incorrect, a magnetic compass aligns itself along the North-South direction, not East-West.

Additional Information

• Magnetic Compass: An instrument containing a magnetized pointer which shows the direction of magnetic north and bearings from it.
• Magnetic Poles: The two ends of a magnet where the magnetic force is strongest; designated as north and south poles.
• Magnetic Field: The region around a magnet where magnetic forces can be observed; Earth's magnetic field influences compass needles.
• Magnetic Repulsion: The force that pushes like poles of magnets apart; for example, north repels north and south repels south.
• North-South Alignment: A fundamental property of compass needles to align with Earth's magnetic field, pointing towards the magnetic north and south poles.

The correct answer is the Direction of the magnetic field.

Key Points

Fleming's Right-Hand Rule:

• Thumb: It is along the direction of motion of the conductor.
• Middle Finger: Indicates the direction of the induced current.
• Index Finger(forefinger):  Indicates the direction of the magnetic field.

Image: Fleming's Right-Hand Rule

Fleming's Left-Hand Rule:

• Thumb: It points towards the direction of motion (force)
• Middle Finger: It represents the direction of the induced current
• Index Finger:  It represents the direction of the magnetic field.   

Important Points 

• Fleming's left-hand rule is used for electric motors.
• Fleming's Right-Hand Rule is used for electric generators

CONCEPT :

• Magnetic materials are broadly classified into

1. Paramagnetic
2. Diamagnetic
3. Ferromagnetic based on the intensity of magnetization

• The given table below shows the behavior of each material in the external magnetic field.

EXPLANATION:

From the above explanation, we can see that

• Air is an example of paramagnetic material since under an external magnetic field it forms an electric dipole.

Additional Information

Properties of paramagnetic materials:

1) When removing the magnetizing field, the paramagnetic material lose their magnetization.

2) Paramagnetic materials have weak magnetization along the direction of the magnetic field.

3) The magnetic lines of force prefer to pass through these materials.

4) The magnetic permeability of paramagnetic materials is slightly greater than one.

The correct answer is the Dynamo effect.

Explanation:

The correct answer is the Dynamo effect.

The Dynamo effect:

• It is a theory that explains the origin of the Earth's main magnetism in terms of a self-sustaining dynamo.
• In this dynamo mechanism, fluid motion in the Earth's outer core moves conducting material (liquid iron) across an already existing, weak magnetic field and generates an electric current.
• The electric current, in turn, produces a magnetic field that also interacts with the fluid motion to create a secondary magnetic field.
• Together, the two fields are stronger than the original and lie essentially along the axis of the Earth's rotation.

The Doppler Effect:

• The Doppler effect is the change in frequency of a wave with respect to an observer who is moving relative to the wave source.
• The changing pitch of the train siren is the best example of the Doppler effect.

The Magnus effect:

• The Magnus effect is related to the spinning bodies (either cylinder or sphere)
• When a soccer player kicks a ball off-centre it causes the ball to spin due to the Magnus effect.

The correct answer is zero.

• Magnetism at the centre of Bar magnet is zero.

​

• Magnetism maxima and minima for a bar magnet
  • Magnetism is strongest at the north poles and south poles of the magnet and weakest at the centre of a bar magnet.
  • This is because the magnetic field lines run parallel to the length of the magnet at the centre and run closer and denser at the poles.
    • or it can be thought of as magnetic field lines are originated from a pole and not at the centre of the bar.

​Additional Information

• Magnetism 
  • Magnetism is a phenomenon by the virtue of which there develops an attracting or repulsive force between two magnetic objects.
  • The motion of electrons in atoms gives rise to magnetism.

The Correct Answer is bar magnet.
Key Points

• The solenoid is a long coil containing a large number of close turns of insulated copper wire.
• When electricity is passed through the solenoid, it acts as an electromagnet.
• The magnetic field produced by a current-carrying solenoid is similar to the magnetic field produced by a bar magnet.
• The magnetic field lines inside the solenoid are in the form of parallel straight lines.

A natural magnet is an ore of Iron oxide(Fe₃O₄).

• A natural magnet is a magnet which occurs naturally in nature.
• All-natural magnets are permanent magnets, which means they can never lose their magnetic strength.
• Strong magnets can be found in sandy soils in various parts of the world.
• Lodestone, also called magnetite, is the best natural magnet substance.
• The stone is black in colour and very smooth when polished.
• The lodestone was originally used in the very first compass ever made.

CONCEPT:

• Solenoid: A cylindrical coil of many tightly wound turns of insulated wire with a general diameter of the coil smaller than its length is called a solenoid.

• A magnetic field is produced around and within the solenoid.
• The magnetic field within the solenoid is uniform and parallel to the axis of the solenoid.

The strength of the magnetic field in a solenoid is given by:-

\(B=\frac{{{\mu }_{0}}NI}{l}\)

Where, N = number of turns, l = length of the solenoid,  l = current in the solenoid and μo = absolute permeability of air or vacuum.

EXPLANATION:​

• The magnetic field inside a solenoid is uniform. So option 2 is correct.

CONCEPT:

• Fleming Left-hand rule gives the force experienced by a charged particle moving in a magnetic field or a current-carrying wire placed in a magnetic field.
  • This rule was originated by John Ambrose Fleming.
  • It is used in an electric motor.
  • It states that "stretch the thumb, the forefinger, and the central finger of the left hand so that they are mutually perpendicular to each other. If the forefinger points in the direction of the magnetic field, the central finger points in the direction of motion of charge, then the thumb points in the direction of force experienced by positively charged particles."

EXPLANATION:

• In Fleming's left rule, the middle finger represents the direction of current flowing through the conductor. So option 3 is correct.
• The thumb represents the direction of the magnetic force.
• The forefinger represents the direction of the magnetic field.

The correct answer is High Resistance in series.

• A Galvanometer is an electromechanical measuring instrument for electric current. 

Key Points

• On the other hand, the voltmeter is an instrument used for measuring the electric potential difference between two points in an electric circuit.
• A galvanometer can be converted into a voltmeter by connecting high resistance (R) in series with the coil of the galvanometer.
• The scale is calculated in volt and the value of the resistance connected in series decides the range of the voltmeter.

CONCEPT:

• Solenoid: A solenoid is a conducting wire wound into coils of many turns forming a cylindrical shape such that its diameter is less compared to its length.
  • Each turn of the coil is treated as a closed circular loop, hence the magnetic field produced from it is considered as that produced by a circular current-carrying conductor.

\(B={{{\mu }_{0}}NI}\)

Where N = number of turns per unit length, l = current in the solenoid, and μo = absolute permeability of air or vacuum.

The field lines due to current in a circular loop are as follows:

• The net magnetic field in a solenoid is, therefore, equal to the vector sum of the magnetic field due to each loop.

EXPLANATION:

• The magnetic field line is a straight line inside a solenoid. Hence, it remains uniform along its length.
• The magnetic field inside a solenoid is the sum of magnetic fields due to all loops. So, on increasing the number of loops, the number of electrons causing current increases. Thus magnetic field strength increases.
• The distance from the current-carrying conductor and the magnetic field are inversely proportional. Thus, towards the ends of the solenoid, the magnetic field strength reduces as they diverge.
• The magnetic field outside the solenoid is zero.