The comprehensive approach in SCERT Class 10 Physics Solutions Chapter 4 Magnetic Effect of Electric Current Important Questions with Answers ensure conceptual clarity.
SSLC Physics Chapter 4 Important Questions Kerala Syllabus
Magnetic Effect of Electric Current Class 10 Important Questions
Question 1.
Find out the odd one and write down the reason. (Paper diaphragm, voice coil, split rings, field magnet)
Answer:
Split rings.
Split rings are part of the electric motor. The paper diaphragm, voice coil, and field magnet are parts of the moving coil loudspeaker.
Question 2.
Write down the factors affecting the direction of force experienced in a current carrying conductor?
Answer:
- Direction of current
- Direction of magnetic field
Question 3.
The mechanism used to vary the direction of current through the armature after each rotation in the motor is ………………….
Answer:
Split ring commutator
Question 4.
Find the first word pair relation and complete the second word pair.
Electric motor: Motor principle
Moving coil loudspeaker: …………………..
Answer:
Motor principle
Question 5.
The magnetic field around the current carrying conductor AB is depicted.
Based on the maxwell’s Right Hand thumb rule find out the direction of current and record it.
Answer:
From B to A to
Question 6.
When electricity flows through a straight conductor, the rule used to detect the direction of the magnetic field around it is ….
Answer:
Right hand thumb rule
Question 7.
An insulated conductor wound in a spiral shape a …………………….
Answer:
Solenoid
Question 8.
In the right hand thumb rule, the thumb indicates the direction of ………………………
Answer:
Direction of current
Question 9.
………………… helps in the continuous rotation of armature in the motor.
Answer:
Split ring commutator
Question 10.
Which are the moving parts of a moving coil loudspeaker?
Answer:
Voice coil, diaphragm
Question 11.
What are the methods to increase the magnetic strength of a current carrying solenoid?
Answer:
- Increase the number of turns of the conductor per unit length.
- Increase the strength of current in the solenoid
- Introduce a soft iron core and increase its area of cross section
Question 12.
a) What happens when we place a magnetic compass nearer to current carrying conductor?
b) Give reason
Answer:
a) Needle of the magnetic compass deflects
b) It is due to the interaction (repulsion) between the magnetic field of the magnetic compass and that of the magnetic field produced by current flow.
Question 13.
Which is the rule that will help to find out the direction of motion of the conductor in the devices making use of magnetic effect of electricity? State the rule.
Answer:
Fleming’s Left Hand Rule.
Hold the thumb, first finger, and second finger of your left hand perpendicular to each other. If the First finger points in the direction of the magnetic field and the second finger in the direction of the electric current, then the thumb will indicate the direction of the force experienced by the conductor.
Question 14.
How will you determine the polarity when the current is passed through a solenoid?
Answer:
The end of the solenoid at which current flows in the clockwise direction will be the south pole and the end at which current flows in the anticlockwise direction will be the North pole.
Question 15.
The direction of movement of electrons through a magnetic field is depicted.
“The force felt by the electrons due to the influence of the magnetic field is into the plane of paper”. Is this statement correct? Explain based on the Fleming’s Left Hand Rule.
Answer:
Yes.
Current flows in the opposite direction of flow of electrons. According to Fleming’s Left Hand Rule, When we hold the forefinger (First finger) in the direction of magnetic field, and the middle finger (second finger) in the direction of current, the thumb points downward into the plane of paper.
Question 16.
In an experiment to know the intensity of magnetic field around a current carrying coil, why is the coil kept in the North South Direction.
Answer:
Only when the coil is kept in the North south direction, the magnetic needle becomes free to move. The coil is kept in the north south direction so as the earth’s magnetic field does not affect the experiment.
Question 17.
In the split ring commutator of a DC motor, semicircular rings are used. What is the need for this?
Answer:
1 n a motor, the split ring commutator rotates along with the armature. The position of the half rings in the split ring commutator changes continuously. So, the direction of current through the coil changes after every half rotation. Thus, continuous rotation is possible in a motor.
Question 18.
A current carrying solenoid is stretched to increase the distance between the coils. What change will occur in its magnetic field? Describe.
Answer:
The strength of magnetic field decreases. As the number of magnetic field lines per unit area decreases, magnetic strength decreases.
Question 19.
State the Motor principle. If the directions of current in the conductor and the magnetic field are the same, in which way will the conductor move?
Answer:
A current carrying conductor which is free to move, placed in a magnetic field, exhibits a tendency to deflect. This is motor principle.
If the current in the conductor and the magnetic field are the same, the conductor will not move.
Question 20.
List the appliances in which electromagnetism is being utilised.
Answer:
Electric motor, generator, electromagnetic relay, Electric bell, Electric fan, Tape recorder, magnetic crane, MCB, ELCB.
Question 21.
A conductor which is kept in a magnetic field experiences a force.
a) Name two devices based on this?
b) Which rule helps us to find direction of motion of the conductor. .
Answer:
a) Mixie, Electric bell, Electric fan
b) Fleming’s left hand rule
Question 22.
Find out the polarity of P and Q.
Answer:
P-Southpole
Q-North pole
Question 23.
The magnetic field of which magnets are depicted? Explain.
Answer:
(a) Bar magnet (b) Electromagnet
The magnetic field lines of the bar magnet and that of the electromagnet are similar. The magnetic strength / magnetism of an electromagnet is temporary and that of a bar magnet is permanent.
Question 24.
Current flowing through a solenoid is represented below.
a) What is the polarity at A ?
b) What is the polarity at B?
Answer:
a) North pole
b) South pole
Question 25.
Observe the figure
a) If current flows from A to B, find the direction of deflection of conductor AB.
(inward, outward)
b) Which is the law that helps you to find the direction of deflection of the conductor.
Answer:
a) Inwards
b) Fleming’s left hand rule
Question 26.
Correct the following
a) Electric motors convert mechanical energy into electrical energy
b) In a moving coil loudspeaker thick wire is used in voice coil.
Answer:
a) Electric motors convert electrical energy into mechanical energy
b) In a moving coil loudspeaker thin wire is used in voice coil
Question 27.
The following statements in the’bekiSs are related to the working of a loudspeaker. Arrange them in the correct order.
Answer:
Question 28.
Write down the working of a moving coil loudspeaker.
Answer:
The moving coil loudspeaker is a device that works based since motor principle The electric signals (audio signals) received from a microphone are amplified using an amplifier. These audio signals are then passed through a voice coil, which is placed in a magnetic field. The coil experiences a force and vibrates because the coil carrying the electric current is placed in a magnetic field. This vibration causes the diaphragm to vibrate, thus reproducing the sound.
Question 29.
Below are some of the characteristics associated with the bar magnet and a current carrying solenoid. Classify them and complete the table.
• Magnetism is temporary.
• Magnetism is permanent
• The magnetic poles cannot be interchanged
• The magnetic strength cannot be varied.
• The magnetic strength can be varied.
• The magnetic pole can be interchanged
Answer:
| Bar magnet | Current carrying solenoid |
| Magnetism is permanent | Magnetism is temporary |
| The magnetic poles cannot be interchanged | The magnetic pole can be interchanged |
| The magnetic strength cannot be varied. | The magnetic strength can be varied |
Question 30.
Write down whether the given statements are correct or wrong. Correct the incorrect statement.
a) If the direction of the current is clockwise at one end of the solenoid, then that end will be north pole.
b) If the direction of the current is anticlockwise at one end of the solenoid, then that end will be south pole.
c) In a moving coil loudspeaker, the electrical energy is converted into sound energy.
Answer:
a) Incorrect statement
If direction of the current is clockwise at one end of the solenoid, then that end will be the south pole.
b) Incorrect statement
If direction of the current is anticlockwise at one end of the solenoid, then that end will be the north pole.
c) Correct
Question 31.
The direction of flow of electrons in a magnetic field is represented.
a) Find the direction of force experienced by electrons (Into the paper, out of the paper)
b) State the law which helped to find the direction of force experienced by electrons.
Answer:
a) Out of the paper
b) Fleming’s left hand rule
Hold the thumb, first finger, and second finger of your left hand perpendicular to each other. If the First finger points in the direction of the magnetic field and the second finger in the direction of the electric current, then the thumb will indicate the direction of the force experienced by the conductor.
Question 32.
Observe the diagram
a) Write the name of this device.
b) Write the energy conversion in this device
c) What is the name of the part ABCD in this device?
Answer:
a) Electric motor
b) Electrical energy is converted into mechanica energy
c) Armature
Question 33.
A moving coil loudspeaker converts electrical energy into sound energy
a) Where is the voice coil situated?
b) Where does the current reach voice coil?
c) To which part is diaphragm connected?
Answer:
a) In between the magnetic poles
b) From amplifier current reaches the voice coi
c) To the voice coil
Question 34.
Observe the figure
a) In which direction does the north pole of the magnetic needle deflect when the switch in the circuit is turned ON? (Clockwise direction/ anticlockwise direction)
b) Suggest two ways to make the direction of the north pole of the magnetic needle in the opposite direction.
Answer:
a) Anticlockwise direction
b)
- Reverse the current
- Arrange the conducting wire AB below the magnetic needle.
Question 35.
Observe the figure
a) When the current is from A to B, in which direction does the north pole of each magnetic needle deflect? (Clockwise direction/ anticlockwise direction)
b) What law helps you to find this out?
c) State the law.
Answer:
a) Anticlockwise direction
b) Right hand thumb rule
c) Imagine holding a conductor with your right hand in such a way that the thumb points in the direction of the electric current, the fingers curled around the conductor will indicate the direction of the magnetic field.
Question 36.
Observe the picture.
a) Which device is represented by the diagram?
b) What is the importance of using a split ring commutator in this device?
c) What are the main parts of this device?
Answer:
a) DC Motor
b) The split ring commutator is used to vary the direction of current through the armature after each half rotation.
c) Magnetic poles, split ring commutator, graphite brushes, armature
Question 37.
Current is passed from South to North through a conductor placed below a freely pivoted magnetic
needle.
a) To which direction will the North Pole of the magnetic needle turn?
b) Which is the rule used to arrive at this inferences?
c) State the rule
d) If the current flows in the conductor in the East West direction, what do you guess about the deflection of the magnetic needle? Explain.
Answer:
a) To the east (in the clockwise direction)
b) Right hand thumb Rule
c) The Right Hand Thumb Rule of James Clerk Maxwell.
Imagine holding a conductor with your right hand in such a way that the thumb points in the direction of the electric current, the fingers curled around the conductor will indicate the direction of the magnetic field.
d) It will be in rest. The direction of magnetic field of the magnetic needle and the direction of magnetic field in the current flowing conductor are same.
Question 38.
Arrange a circuit above a pivoted magnetic needle in such a way that the part AB of the conductor is parallel and close to the magnetic needle, as shown in Figure.
Switch on the circuit. Observe the direction in which the North Pole (N) of the magnetic needle deflects and answer the following questions.
a) When the direction of electric current is from A to B(in figure (a)), what will be the direction of the electron flow through it?
b) Based on figure (a) and (b) complete the below given table.
| No. | Conductor above the magnetic needle | Direction of motion of North Pole (N) of the magnetic needle clockwise/anticlo ckwise |
| 1 | Direction of current from A to B | |
| 2 | Direction of current from B to A |
c) Repeat the experiment by keeping the conductor below the magnetic needle and record the observations in the table.
d) What might be the reason for the deflection of the magnetic needle?
e) Does the deflection depend on the direction of current?
Answer:
a) From B to A
b)
| No. | Conductor above the magnetic needle | Direction of motion of North Pole (N) of the magnetic needle clockwise/anticlo ckwise |
| 1 | Direction of current from A to B | Anticlockwise |
| 2 | Direction of current from B to A | clockwise |
c)
| No. | Conductor below the magnetic needle | Direction of motion of North Pole (N) of the magnetic needle clockwise/anticlo ckwise |
| 1 | Direction of current from A to B | clockwise |
| 2 | Direction of current from B to A | Anticlockwise |
d) A magnetic field is developed around a current carrying conductor. The magnetic needle is deflected as a result of the mutual action of this magnetic field and that around the magnetic needle.
e) Yes
Question 39.
Observe the picture and answer the questions.
a) What happens to the air column around the paper cone when the voice coil vibrates?
b) Does the voice coil vibrate if DC reaches the voice coil?
c) What is the working principle?
d) Mention the energy change taking place.
Answer:
a) Air column also vibrates. As a result, sound is produced.
b) No. Because there is no flux change occurring.
c) Motor principle
d) Electrical energy to sound energy
Question 40.
The direction of magnetic field lines around the current carrying conductor AB is represented.
a) Find the direction of flow of current
b) Which rule helped you to find the direction of flow of current
c) State the rule
Answer:
a) From A to B
b) Right hand thumb rule
c) Imagine holding a conductor with your right hand in such a way that the thumb points in the direction of the electric current, the fingers curled around the conductor will indicate the direction of the magnetic field.
Question 41.
Observe the figure and answer the following questions
a) If the direction of current flow is from A to D, then what will be the direction of rotation of armature ?(clockwise direction, anticlockwise direction)
b) Justify your answer
c) What is the name of the parts R, and Rr What is its function?
Answer:
a) Anticlockwise direction
b) According to Fleming’s left hand rule, middle finger when held in the direction of current and forefinger when held in the direction of magnetic field, then the thumb indicates the direction of motion of conductor AB. The direction of motion is downwards, so coil ABCD rotates in anticlockwise direction
c) R1 and R2 are the split rings
For each half rotation of armature, the direction of current through the armature changes as the position of the split rings interchanges. Therefore armature keeps on rotating continuously.
Question 42.
A circuit showing a solenoid connected to a cell is given below.
a) When switched ON, what is the polarity at end A ?
b) When switched ON, what is the polarity at end B ?
c) Write two methods to increase the magnetic strength of a current carrying solenoid?
Answer:
a) South pole
b) North pole
c)
- Increase the number of turns of the conductorper unit length.
- Increase the strength of current in the solenoid or increase the number of cells.
Question 43.
Check if the given statements are correct or incorrect. Correct the incorrect statements.
i. The direction of magnetic flux lines inside a bar magnet is from north pole to south pole.
ii. If the current in the coil is clockwise, the direction of the flux lines will be inward into the coil.
Answer:
i. Incorrect statement
The direction of magnetic flux lines inside a bar magnet is from the south pole to north pole.
ii. Correct statement
Question 44.
The direction of current through a straight conductor AB is shown figure.
What is the direction of the magnetic field at the points P and Q?
Answer:
P – Out of the plane of the paper
Q – Into the plane of the paper.
Question 45.
A straight conductor AB is arranged parallel to a magnetic needle as shown in the figure. When the switch is on, the magnetic needle deflects.
a) The direction in which the North pole of the magnet deflects is: …(Clockwise / Anticlockwise). Name the law used to find the direction of deflection of the needle?
b) What is the reason for the deflection of the needle?
c) Suggest a method to reverse the direction of deflection of the magnetic needle?
Answer:
a) Anticlockwise direction.
Right-hand thumb rule
b) When a current is passed through the conductor, a magnetic field is produced around it.
c) Reverse the direction of the current.
b) Right hand thumb rule
Figure shows a circular coil carrying current. Draw the magnetic field line through the centre of the coil.
Question 46.
A conductor is inserted through a cardboard and kept in a vertical position as in the figure.
The portions passing through the cardboard are marked as X and Y.
a) Mark the direction of magnetic field around the points X and Y.
b) Name the law used to find the direction of magnetic field.
Answer:
b) Right hand thumb rule
Question 47.
Figure shows a circular coil carrying current. Draw the magnetic field line through the centre of the
coil.
Answer:
Question 48.
The figure shows a bar magnet arranged near a solenoid. When the switch is put on, will the solenoid attract or repel the bar magnet? What is the reason?
Answer:
Attracts. Since the current is in a clockwise direction, the end of A is the South Pole.
Question 49.
What distinguishes the magnetic field of a permanent magnet, like a bar magnet, from that of an electromagnet?
Answer:
The magnetic field of a permanent magnet is fixed, while an electromagnet’s field is temporary and can be controlled by adjusting the current flow. The polarity of bar magnet cannot be changed whereas that of electromagnet can be changed by changing the direction
Question 50.
What happens when current passes through a solenoid? What happens when soft iron core is inserted into it.
Answer:
The solenoid behaves like an electromagnet exhibiting magnetic properties. Strength of solenoid increases when soft iron core is inserted into it.
Question 51.
Write any two situations where strong electromagnets are used ?
Answer:
- MRI scanner
- Cranes using electromagnets
Question 52.
Explain why the direction of current through the armature needs to change continuously for sustained rotation?
Answer:
Continuous change in the direction of current through the armature ensures that the forces acting on its sides remain in the same direction, sustaining its rotation. The split ring commutator facilitates this change in the current direction.
Question 53.
What role does Fleming’s Left Hand Rule play in understanding the motion of the conductor in an electric motor?
Answer:
Fleming’s Left Hand Rule helps in determining the direction of motion of the conductor in devices utilizing the magnetic effect of electricity, such as electric motors.
Question 54.
In an electric motor, electrical energy is converted into ….
Answer:
Mechanical energy
Question 55.
ABCD is a rectangular coil arranged so as to move freely in a magnetic field.
a) In which direction will the coil rotate when a current is passed through the coil in the direction ABCD?
b) Why commutator is necessary for the continuous rotation of the coil?
Answer:
a) Anticlockwise direction.
b) If the rotation of the armature is to be sustained, the direction of current through the armature should change continuously. The split rings help to change the direction of current through the coil after every half rotation.
Question 56.
Statements regarding the working of a moving coil loudspeaker are given below. Rearrange them in the correct sequence.
i. The voice coil placed in the magnetic field moves to and fro rapidly according to the electric pulses.
ii. The diaphragm vibrates and reproduces sound.
iii. The electric pulses from the microphone are strengthened and passed through the voice coil.
Answer:
(iii) → (i) → (ii)
Question 57.
What component of a moving coil loudspeaker is responsible for converting electrical signals into sound waves?
Answer:
The diaphragm, connected to the voice coil, is responsible for converting electrical signals into sound waves.
Question 58.
How does the movement of the voice coil contribute to sound reproduction in a loudspeaker?
Answer:
The rapid movement of the voice coil, induced by electrical pulses in the magnetic field, causes the attached diaphragm to vibrate, thereby reproducing sound.
Question 59.
State true or false. Correct the incorrect statements
a) In a moving coil loudspeaker, sound energy is converted into electrical energy.
b) Voice coil is placed in a magnetic field
Answer:
a) False
Corrected statement: In a moving coil loudspeaker, electrical energy is converted into sound energy.
b) True