Magnetic Effects of Electric Current — Important Questions
47 questions
With answersCBSE format
SUMMARY: This chapter explores the magnetic effects produced by electric currents and the principles behind electromagnetism. KEY TOPICS: Oersted's experiment, magnetic field lines, right-hand thumb rule, electromagnetic induction, electric motor, Fleming's left-hand rule, electromagnetic force, solenoid, magnetic field due to a current-carrying conductor, applications of electromagnets.
AThe relationship between electricity and magnetism
BThe effect of temperature on resistance
CThe principles of electrolysis
DThe behavior of gases under pressure
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Correct answer: Option 1 — The relationship between electricity and magnetism
Q21 Mark
Which rule is used to determine the direction of magnetic field lines around a current-carrying conductor?
AFleming's left-hand rule
BRight-hand thumb rule
CAmpere's law
DFaraday's law
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Correct answer: Option 2 — Right-hand thumb rule
Q31 Mark
What is the shape of the magnetic field lines around a straight conductor carrying current?
AStraight lines
BCircular loops
CElliptical loops
DSpiral lines
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Correct answer: Option 2 — Circular loops
Q41 Mark
In Fleming's left-hand rule, what does the thumb represent?
ADirection of magnetic field
BDirection of current
CDirection of force
DDirection of motion
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Correct answer: Option 3 — Direction of force
Q51 Mark
What is the primary function of an electric motor?
ATo convert electrical energy into mechanical energy
BTo convert mechanical energy into electrical energy
CTo store electrical energy
DTo regulate current flow
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Correct answer: Option 1 — To convert electrical energy into mechanical energy
Q61 Mark
What is the role of a solenoid in electromagnetism?
ATo increase resistance
BTo create a uniform magnetic field
CTo decrease voltage
DTo store magnetic energy
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Correct answer: Option 2 — To create a uniform magnetic field
Q71 Mark
Which of the following statements is true about electromagnetic induction?
AIt occurs only in static magnetic fields
BIt involves the generation of current by changing magnetic fields
CIt requires a constant current
DIt cannot be used in transformers
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Correct answer: Option 2 — It involves the generation of current by changing magnetic fields
Q81 Mark
What happens to the magnetic field strength when the current in a solenoid is increased?
AIt decreases
BIt remains the same
CIt increases
DIt becomes zero
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Correct answer: Option 3 — It increases
Q91 Mark
Which device uses the principle of electromagnetic induction to convert mechanical energy into electrical energy?
ATransformer
BElectric generator
CInductor
DCapacitor
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Correct answer: Option 2 — Electric generator
Q101 Mark
According to the right-hand thumb rule, if you point your thumb in the direction of the current, the fingers curl in the direction of the:
AElectric field
BMagnetic field
CForce applied
DVoltage
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Correct answer: Option 2 — Magnetic field
Q111 Mark
What is the effect of increasing the number of turns in a coil of wire on the strength of the magnetic field produced?
AIt has no effect
BIt weakens the field
CIt strengthens the field
DIt reverses the field direction
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Correct answer: Option 3 — It strengthens the field
Q121 Mark
Which of the following is NOT an application of electromagnets?
AElectric bells
BMagnetic locks
CBatteries
DMRI machines
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Correct answer: Option 3 — Batteries
Q131 Mark
What is the direction of the magnetic field inside a current-carrying solenoid?
AFrom south to north
BFrom north to south
CCircular
DIrregular
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Correct answer: Option 2 — From north to south
Q141 Mark
In an electric motor, the interaction between the magnetic field and the current produces:
AHeat
BLight
CMechanical motion
DChemical reaction
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Correct answer: Option 3 — Mechanical motion
Q151 Mark
What is the primary cause of the magnetic field around a current-carrying conductor?
AThe flow of electrons
BThe resistance of the conductor
CThe voltage applied
DThe temperature of the conductor
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Correct answer: Option 1 — The flow of electrons
Short Answer Questions10 questions
Q163 Marks
What was the main observation of Oersted's experiment regarding electric current and magnetism?
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Oersted observed that an electric current flowing through a wire produces a magnetic field around it, which can influence a nearby compass needle, indicating a relationship between electricity and magnetism.
Q173 Marks
Define magnetic field lines and explain their significance.
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Magnetic field lines are imaginary lines that represent the direction and strength of a magnetic field. They emerge from the north pole of a magnet and enter the south pole, indicating the path a north magnetic pole would take in the field.
Q183 Marks
State the right-hand thumb rule and its application in determining the direction of magnetic field lines.
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The right-hand thumb rule states that if you hold a current-carrying conductor with your right hand, with the thumb pointing in the direction of the current, the curled fingers show the direction of the magnetic field lines around the conductor.
Q193 Marks
What is electromagnetic induction and who discovered it?
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Electromagnetic induction is the process of generating an electromotive force (EMF) in a conductor due to a changing magnetic field. It was discovered by Michael Faraday.
Q203 Marks
Explain the working principle of an electric motor.
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An electric motor works on the principle of the interaction between a magnetic field and a current-carrying conductor. When current flows through the coil in the magnetic field, it experiences a force that causes it to rotate, converting electrical energy into mechanical energy.
Q213 Marks
What does Fleming's left-hand rule help to determine?
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Fleming's left-hand rule helps to determine the direction of force experienced by a current-carrying conductor in a magnetic field. The thumb indicates the direction of force, the forefinger the magnetic field, and the middle finger the direction of current.
Q223 Marks
Describe the concept of electromagnetic force and its significance.
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Electromagnetic force is the force exerted on a charged particle moving through a magnetic field. It is significant because it is responsible for the operation of electric motors, generators, and many other electrical devices.
Q233 Marks
What is a solenoid and how does it create a magnetic field?
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A solenoid is a long coil of wire wound in the form of a helix. When an electric current passes through it, a magnetic field is generated inside the solenoid, resembling that of a bar magnet, with distinct north and south poles.
Q243 Marks
How does the magnetic field due to a current-carrying conductor vary with distance from the conductor?
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The magnetic field strength around a current-carrying conductor decreases with increasing distance from the conductor. It follows an inverse relationship, where the field strength is stronger closer to the wire and weaker further away.
Q253 Marks
List two applications of electromagnets in everyday life.
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Electromagnets are used in various applications such as in electric bells, where they help in ringing the bell, and in magnetic cranes, which lift heavy metal objects in scrap yards.
Long Answer Questions6 questions
Q266 Marks
Explain Oersted's experiment and its significance in establishing the relationship between electricity and magnetism.
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Oersted's experiment demonstrated that an electric current flowing through a conductor produces a magnetic field around it. He conducted an experiment where he placed a compass near a wire carrying current and observed that the compass needle deflected, indicating the presence of a magnetic field. This experiment was significant as it established the foundational principle of electromagnetism, showing that electric currents can create magnetic fields, which is a fundamental concept in physics and has numerous applications in technology.
Q276 Marks
Describe the concept of magnetic field lines and how they are used to represent magnetic fields.
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Magnetic field lines are imaginary lines used to represent the direction and strength of a magnetic field. They emerge from the north pole of a magnet and enter the south pole, forming closed loops. The density of these lines indicates the strength of the magnetic field; closer lines signify a stronger field. Additionally, the direction of the field lines indicates the direction of the magnetic force experienced by a north pole placed in the field. This concept is crucial for visualizing magnetic fields and understanding their behavior in various applications.
Q286 Marks
What is the right-hand thumb rule? Explain its application in determining the direction of the magnetic field around a current-carrying conductor.
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The right-hand thumb rule is a mnemonic used to determine the direction of the magnetic field around a straight current-carrying conductor. According to this rule, if you hold the conductor with your right hand such that your thumb points in the direction of the current, then your curled fingers will point in the direction of the magnetic field lines. This rule is essential for visualizing the orientation of magnetic fields in practical applications like electric motors and generators.
Q296 Marks
Define electromagnetic induction and describe its principle with an example.
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Electromagnetic induction is the process by which a changing magnetic field induces an electromotive force (EMF) in a conductor. The principle of electromagnetic induction was discovered by Michael Faraday, who stated that a change in magnetic flux through a circuit induces an EMF in that circuit. For example, when a magnet is moved towards a coil of wire, the changing magnetic field induces a current in the wire. This principle is the basis for the operation of generators and transformers, making it crucial in electrical engineering.
Q306 Marks
Discuss the working principle of an electric motor and the role of Fleming's left-hand rule in its operation.
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An electric motor converts electrical energy into mechanical energy using the interaction between a magnetic field and a current-carrying conductor. When current flows through the motor's coil placed in a magnetic field, it experiences a force due to the magnetic field, causing it to rotate. Fleming's left-hand rule helps predict the direction of this force; if the thumb represents the direction of the force (motion), the index finger represents the magnetic field, and the middle finger represents the current. This rule is fundamental in understanding how motors operate and is widely applied in various devices.
Q316 Marks
Explain the concept of electromagnetic force and its significance in the context of electric circuits.
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Electromagnetic force (EMF) is the energy provided per unit charge by an energy source in an electric circuit. It is significant because it drives the flow of electric current through the circuit. EMF can be generated by various means, including batteries, generators, and solar cells. Understanding EMF is crucial for analyzing and designing electrical circuits, as it determines how much current can flow based on the resistance in the circuit. This concept is fundamental in both theoretical and practical applications of electricity.
Assertion–Reason Questions8 questions
Q321 Mark
Assertion (A): Oersted's experiment demonstrated that an electric current produces a magnetic field.
Reason (R): The magnetic field lines form concentric circles around the current-carrying conductor.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q331 Mark
Assertion (A): The right-hand thumb rule can be used to determine the direction of the magnetic field around a current-carrying wire.
Reason (R): The thumb represents the direction of the current, while the fingers show the direction of the magnetic field lines.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q341 Mark
Assertion (A): Electromagnetic induction occurs when a magnetic field is changed near a conductor.
Reason (R): This change induces an electromotive force (EMF) in the conductor.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q351 Mark
Assertion (A): Fleming's left-hand rule is used to determine the direction of force on a conductor in a magnetic field.
Reason (R): It applies only to electric motors and not to generators.
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Correct answer: Option 3 —
A is true, but R is false.
Q361 Mark
Assertion (A): A solenoid creates a uniform magnetic field when an electric current passes through it.
Reason (R): The magnetic field inside a solenoid is stronger than outside it.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q371 Mark
Assertion (A): The magnetic field due to a straight current-carrying conductor is uniform.
Reason (R): The field lines are parallel and equally spaced.
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Correct answer: Option 4 —
A is false, but R is true.
Q381 Mark
Assertion (A): Electromagnets are used in electric motors to convert electrical energy into mechanical energy.
Reason (R): They can be turned on and off, providing control over the motor's operation.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q391 Mark
Assertion (A): The strength of the magnetic field around a conductor increases with the increase in current.
Reason (R): This is due to the increased number of magnetic field lines generated.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Statement-Based Questions8 questions
Q401 Mark
Statement 1: Oersted's experiment demonstrated that an electric current produces a magnetic field.
Statement 2: The direction of the magnetic field can be determined using Fleming's left-hand rule.
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Correct answer: Option 1 —
Both statements are true.
Q411 Mark
Statement 1: Magnetic field lines can intersect each other in a magnetic field.
Statement 2: The right-hand thumb rule helps in determining the direction of the magnetic field around a current-carrying conductor.
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Correct answer: Option 3 —
Only Statement 2 is true.
Q421 Mark
Statement 1: A solenoid is a coil of wire that produces a uniform magnetic field when an electric current passes through it.
Statement 2: Electromagnetic induction is the process of generating an electric current from a changing magnetic field.
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Correct answer: Option 1 —
Both statements are true.
Q431 Mark
Statement 1: Fleming's left-hand rule is used to find the direction of force on a current-carrying conductor in a magnetic field.
Statement 2: The magnetic field due to a current-carrying conductor is always directed from north to south.
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Correct answer: Option 2 —
Only Statement 1 is true.
Q441 Mark
Statement 1: An electric motor converts electrical energy into mechanical energy using the principle of electromagnetism.
Statement 2: The strength of the magnetic field produced by a solenoid is independent of the amount of current flowing through it.
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Correct answer: Option 4 —
Both statements are false.
Q451 Mark
Statement 1: The magnetic field lines around a straight current-carrying conductor are circular in shape.
Statement 2: Oersted's experiment was conducted to prove that magnetic fields can exist without electric currents.
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Correct answer: Option 2 —
Only Statement 1 is true.
Q461 Mark
Statement 1: Electromagnets can be turned on and off by controlling the electric current.
Statement 2: The right-hand thumb rule is applicable for determining the direction of force in electric motors.
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Correct answer: Option 1 —
Both statements are true.
Q471 Mark
Statement 1: The magnetic field inside a solenoid is uniform and parallel to the axis of the solenoid.
Statement 2: The direction of the magnetic field lines is from the south pole to the north pole outside the magnet.
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Correct answer: Option 1 —
Both statements are true.
