Critical Thinking Questions: Electromagnetism

​Type I

Assertion & Reason Based Questions

Q1: Assertion: The strength of the magnetic field created by a current-carrying wire decreases as the distance from the wire increases.
Reason: The magnetic field strength is inversely proportional to the square of the distance from the source due to the magnetic field lines spreading out as they move away from the wire.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Q2: Assertion: Increasing the number of turns in a solenoid increases the strength of the magnetic field.
Reason: More turns in the solenoid reduce the resistance of the coil, which increases the magnetic field strength.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Q3: Assertion: A current-carrying loop of wire behaves as a magnetic dipole.
Reason: The magnetic field lines through the loop of wire resemble those of a bar magnet, with distinct north and south poles.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Q4: Assertion: An electric bell uses an electromagnet to function.
Reason: In an electric bell, the electromagnet is used to create a repetitive motion to strike the gong due to the make and break of the circuit.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Q5: Assertion: A permanent magnet can retain its magnetism indefinitely if it is made of a material with high magnetic coercivity.
Reason: Permanent magnets are often made of steel, which has higher magnetic retentivity compared to soft iron.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) Both the assertion and the reason are true, but the reason is not a correct explanation of the assertion. 
(c) The assertion is true, but the reason is false. 
(d) The assertion is false, but the reason is true.

Q6: Assertion: The armature coil in a simple DC motor continues to rotate due to inertia even when there is momentarily no contact between the brushes and the commutator.
Reason: The continuous rotation is due to the torque generated by the current in the coil, which persists even in the absence of a continuous electrical connection.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) Both the assertion and the reason are true, but the reason is not a correct explanation of the assertion. 
(c) The assertion is true, but the reason is false. 
(d) The assertion is false, but the reason is true.

Q7: Assertion: Electromagnetic induction occurs only when there is a change in the number of magnetic field lines passing through a coil.
Reason: A stationary magnet inside a coil induces no current because it does not change the magnetic flux through the coil.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Q8: Assertion: The induced e.m.f. in a coil rotating within a magnetic field is maximum when the plane of the coil is parallel to the magnetic field.
Reason: This is because when the plane of the coil is parallel to the magnetic field, the rate of change of magnetic flux linked with the coil is greatest.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Q9: Assertion: Fleming's right-hand rule is used to find the direction of the induced current in a conductor moving in a magnetic field.
Reason: The right-hand rule involves orienting the thumb, forefinger, and middle finger perpendicular to each other, where the thumb represents the direction of the conductor's motion.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Q10: Assertion: The frequency of the alternating current in a household supply can be increased by increasing the speed of rotation of the coil in the generator.
Reason: According to the formula e = e₀sin(2πnt), where n is the number of rotations per second, increasing n will result in an increase in the frequency of the generated e.m.f.
(a) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion. 
(b) The assertion is true, but the reason is false. 
(c) The assertion is false, but the reason is true. 
(d) Both the assertion and the reason are false.

Type II

Statements Based Questions

Q11: Statement 1: The experiment demonstrated that an electric current produces a magnetic field. 
Statement 2: The direction of the magnetic field changes with the direction of the current. 
Statement 3: A compass needle is unaffected by the current in a nearby wire.
(a) Only 1 and 2 
(b) Only 1 
(c) Only 2 and 3 
(d) All 1, 2, and 3

Q12: Statement 1: Magnetic field lines around a straight conductor are parallel to the wire. 
Statement 2: Reversing the current direction reverses the direction of the magnetic field. 
Statement 3: Increasing the current strength increases the density of the magnetic field lines.
(a) Only 2 and 3 
(b) Only 1 and 3 
(c) Only 1 
(d) All 1, 2, and 3

Q13: Statement 1: Electromagnets lose their magnetism when the electric current is stopped. 
Statement 2: The strength of an electromagnet can be increased by increasing the current. 
Statement 3: Electromagnets can have their polarity reversed by reversing the current.
(a) Only 1 and 2 
(b) Only 2 and 3 
(c) Only 1 and 3 
(d) All 1, 2, and 3

Q14: Statement 1: The magnetic field inside a solenoid is uniform. 
Statement 2: The strength of the magnetic field in a solenoid depends on the coil's diameter. 
Statement 3: Reversing the current direction in a solenoid reverses its magnetic field.
(a) Only 1 and 3 
(b) Only 1 
(c) Only 2 and 3 
(d) All 1, 2, and 3

Q15: An electrician from Urban Company is working at your house with a simple electric motor in a ceiling fan. The motor contains a current-carrying wire loop that rotates in a magnetic field.
Statement 1: When the technician increases the current in the wire loop, the rotational force on the loop also increases. 
Statement 2: Changing the orientation of the wire loop relative to the magnetic field changes the direction of rotation. 
Statement 3: The rotational force on the loop is less if the loop is made longer, keeping the current and magnetic field constant.
(a) Only 1 and 2 
(b) Only 2 
(c) Only 1 
(d) All 1, 2, and 3

Q16: Consider a simple electric train set. The train (which is essentially a current-carrying conductor) moves on a track that has a magnetic field.
Statement 1: The speed of the train is proportional to the amount of current supplied. 
Statement 2: The direction in which the train moves depends on the direction of the magnetic field. 
Statement 3: The speed of the train is inversely proportional to the length of the train.
(a) Only 1 
(b) Only 1 and 2 
(c) Only 2 
(d) All 1, 2, and 3

Q17: Statement 1: Electromagnetic induction occurs when a conductor moves through a stationary magnetic field. 
Statement 2: Changing the magnetic field around a stationary conductor induces current. 
Statement 3: Induced current is always in the same direction as the movement of the conductor.
(a) Only 1 and 2 
(b) Only 2 
(c) Only 1 
(d) All 1, 2, and 3

Q18: Statement 1: An electromagnet can be demagnetised by turning off the electric current. 
Statement 2: A permanent magnet can easily change its magnetic field strength. 
Statement 3: The polarity of an electromagnet can be reversed by changing the direction of the current.
(a) Only 1 and 3 
(b) Only 2 
(c) Only 1 
(d) All 1, 2, and 3

Q19: Statement 1: In a solenoid, the magnetic field inside is uniform and parallel to its axis. 
Statement 2: The strength of the magnetic field in a solenoid increases with the number of turns of the coil. 
Statement 3: The direction of the magnetic field in a solenoid does not depend on the direction of the current.
(a) Only 1 and 2 
(b) Only 2 
(c) Only 1 
(d) All 1, 2, and 3

Q20: Statement 1: A current carrying wire in a magnetic field experiences a force perpendicular to both the current and the magnetic field. 
Statement 2: The direction of the force on a current-carrying wire in a magnetic field can be determined using Fleming's left-hand rule.
Statement 3: The magnitude of the force on a current-carrying wire in a magnetic field depends only on the strength of the magnetic field.
(a) Only 1 
(b) Only 2 
(c) Only 1 and 2 
(d) All 1, 2, and 3