Case Study Questions Science Class 10th

Chapter 13: Magnetic Effects of Electric Current

Case Study Question 01

Read the following passage carefully and answer the following questions:

Electric Charges moving in a magnetic field experience a force, while there is no such force on static charges. This fact was first recognized by Hendrik Antoon Lorentz, a great Dutch physicist, nearly a century ago. Thus, a charge moving in a magnetic field experience a force, except when it is moving in a direction parallel to it. The magnitude of force experienced depends on the charge, velocity (`v`), strength of magnetic field (`B`), and sine of the angle between `v` and `B`. If the direction of velocity is perpendicular to the direction of magnetic field, direction of magnetic force is given by Fleming’s left hand rule.Case_magnetic_01Case_magnettic_02

Question.1.
If an electron is travelling horizontally towards east. A magnetic field in vertically downward direction exerts a force on the electron along

(a) east
(b) west
(c) north
(d) south.

(d) : Fleming’s left hand rule is used to determine the direction of force on electron i.e., in south direction.

Question.2.
If a charged particle is moving along a magnetic field line. The magnetic force on the particle is

(a) along its velocity
(b) opposite to its velocity
(c) perpendicular to its velocity
(d) zero.

(d) : The angle between velocity and magnetic field is zero. Therefore, magnetic force on the particle is zero.

Question.3.
A uniform magnetic field exists in the plane of paper pointing from left to right as shown in figure. In the field an electron and a proton move as shown. The electron and the proton experienceCase_magnetic_03

(a) forces both pointing into the plane of paper
(b) forces both pointing out of the plane of paper
(c) forces pointing into the plane of paper and out of the plane of paper, respectively
(d) force pointing opposite and along the direction of the uniform magnetic field respectively.

(a) : As the direction of current is taken opposite to the direction of motion of electrons, therefore, current from the motion of electron and proton is in the same direction, i.e., from bottom to top. Now, according to Fleming’s left hand rule, the electron and the proton experience forces both pointing into the plane of paper.

Question.4.
An neutron beam enters a magnetic field at right angles to it as shown in the figure. Due to magnetic field, neutron beam will deflectCase_magnetic_04

(a) to the left
(b) to the right
(c) into the page
(d) no deflection.

(d) : Neutron is uncharged particle so no magnetic force will act on it.

Chapter 13: Magnetic Effects of Electric Current

Case Study Question 02

Read the following passage carefully and answer the following questions:

An electric motor is a rotating device that converts electrical energy into mechanical energy. Electric motor is used as an important component in electric fans, refrigerators, mixers, washing machines, computers, MP3 players, etc.Case_magnetic_04An electric motor consists of a rectangular coil ABCD of insulated copper wire. The coil is placed between the two poles of a magnetic field such that the arm AB and CD are perpendicular to the direction of the magnetic field. The ends of the coil are connected to the two halves P and Q of a split ring. The inner sides of these halves are insulated and attached to an axle. The external conducting edges of P and Q touch two conducting stationary brushes X and Y, respectively, as shown in the figure.
Commercial motors use an electromagnet in place of a permanent magnet.

Question.1.
Choose incorrect statement from the following regarding split rings.

(a) Split rings are used to reverse the direction of current in coil.
(b) Split rings are also known as commutator.
(c) Split ring is a discontinuous or a broken ring.
(d) Both (a) and (b)

(d) Both (a) and (b)

Question.2.
Which of the following has no effect on the size of the turning effect on the coil of an electric motor?

(a) The amount of the current in the coil.
(b) The direction of the current in the coil.
(c) The number of turns in the coil.
(d) The strength of the magnetic field.

(b) : The direction of the current has no effect on the size of the turning effect on the coil.

Question.3.
When current is switched ON, an electric fan converts

(a) mechanical energy to chemical energy
(b) electrical energy to mechanical energy
(c) chemical energy to mechanical energy
(d) mechanical energy to electrical energy.

(b) : Electric fan works on the principle of electric motor. It converts electrical energy to mechanical energy.

Question.4.
In an electric motor, device that makes contact with the rotating rings and through them current is supplied to coil is

(a) axle
(b) brushes
(c) coil
(d) split rings.

(b) brushes

Chapter 13: Magnetic Effects of Electric Current​

Case Study Question 03

Read the passage carefully and answer the following questions:

When a small compass is placed near a magnet, it will experience a force due to the magnetic field of the magnet. It is evidently observed due to a deflection in the north pole pointer of the compass. The path traced by the north pole pointer under the influence of a magnetic field is called the magnetic field line. The magnetic field lines are produced from the north pole of the magnet end at the south pole of the magnet. When the compass is moved around the field line, it always sets itself tangential along the curves.

Question.1.
The magnetic field lines:

(a) intersect at right angle to one another.
(b) intersect at an angle of 45 degree.
(c) cross at an angle of 60 degree.
(d) never intersect with each other.

(d) never intersect with each other.

Question.2.
Magnetic field lines can be used to determine:

(a) the shape of the magnetic field.
(b) only the direction of the magnetic field.
(c) only the relative strength of the magnetic field.
(d) both the direction and the relative strength of the magnetic field.

(d) both the direction and the relative strength of the magnetic field.

Question.3.
The magnetic field lines due to a bar magnet are correctly shown in:

(a)a(b) b(c)c(d)d

Question.4.
Which of the following is incorrect regarding magnetic field lines?

(a) The field lines are directed N to S inside the magnet.
(b) The Crowdedness of the field lines shows the strength of the magnet.
(c) The field is tangent to the magnetic field line.
(d) Magnetic field lines are closed and continuous curves.

(a) The field lines are directed N to S inside the magnet.

Question.5.
A strong bar magnet placed vertically above a surface. The magnetic field lines will be:

(a) Only in a horizontal plane around the magnet.
(b) Only in a vertical plane around the magnet.
(c) Both in horizontal and vertical plane around the magnet.
(d) In all the planes around the magnet.

(d) In all the planes around the magnet

Chapter 13: Magnetic Effects of Electric Current​

Case Study Question 04

Refer the figure below carefully and answer the following questions:

A current-carrying wire produces a magnetic field around it. The phenomena in which an electromotive force and current are induced by changing magnetic field through it is called induced current. It can be concluded that the induced current flows in a conductor as long as the magnetic force changes within the conductor. For the motion of the coil with respect to the magnet or vice versa, the direction of the current flowing in the conductor is determined by the direction of the relative motion of the conductor with respect to the magnetic field. The induced emf or current is directly proportional to the rate of change in the magnetic field.Case_magnetic_05

Question.1.
What is the condition of electromagnetic induction?

(a) There must be relative motion between galvanometer and coil of wire.
(b) There must be a relative motion between galvanometer and magnet.
(c) There must be a relative motion between galvanometer and electric motor.
(d) There must be a relative motion between the coil of wire and a magnet.

(d) There must be a relative motion between the coil of wire and a magnet.

Question.2.
An induced emf is produced when a magnet is plugged into a coil. The magnitude of induced emf does not depend upon:

(a) The number of turns in the coil.
(b) The speed with which the magnet is moved.
(c) The resistivity of the material of the coil.
(d) The strength of the magnet.

(c) The resistivity of the material of the coil

Question.3.
A bar magnet is pushed steadily into a long solenoid connected to a meter. Which of the following would affect the magnitude of the deflection of the meter?

(a) How fast the magnet is pushed into the coil.
(b) Direction in which the coil is wound.
(c) End of the solenoid where the magnet enters.
(d) Pole of the magnet which enters the coil first.

(a) How fast the magnet is pushed into the coil

Question.4.
A conducting rod moves across two magnets as shown in the figure and the needle in the galvanometer deflects momentarily.Case_magnetic_06This physical phenomenon is called:

(a) Induced magnetism
(b) Electromagnetism
(c) Static induction
(d) Electromagnetic induction

(d) Electromagnetic induction

Question.5.
Magnetic lines of force inside current-carrying solenoid are:

(a) perpendicular to axis.
(b) along the axis and are parallel to each other.
(c) parallel inside the solenoid and circular at the ends.
(d) circular.

(b) along the axis and are parallel to each other

Chapter 13: Magnetic Effects of Electric Current

Case Study Question 05

Refer the figure below carefully and answer the following questions:

Hans christian Oersted, one of the leading scientists of the 19th century, play a crucial role in understanding electromagnetism. In 1820, he accidentally discovered that a compass needle got defected when an electric current passed through a metallic wire placed nearly. Through this observation Oersted showed that electricity and magnetic were related phenomenon. This research later created technologies such as radio, television and fibre optics. The unit of magnetic field was named as Oersted in his honour. Electromagnetism is the study of electromagnetic force. It is a type of interface that happens between electrically charged particles. The electromagnetic force generally exhibits electromagnetic fields like magnetic fields, electric fields and light, and is one of the four essential interactions commonly known as forces in nature. The other 3 important interactions are the strong interaction, gravitation and the weak.

Question.1.
Oersted experiment is used to explain which effect of current ?

(a) Electric field
(b) Magnetic field
(c) Both (a) and (b)
(d) None of these

(b) Magnetic field

Explanation: He make to understand that current carrying wire has magnetic field around it.

Question.2.
Which instrument helps to detect the presence of magnetic field at a point?

(a) Strong magnet
(b) Solenoid
(c) Compass needle
(d) Current carrying line

(c) Compass needle

Explanation : Compass needle is a small bar magnet, whose ends are approximately towards the north and south direction.

Question.3.
In the diagram below, the direction of magnetic field is:Case_magnetic_07

(a) Clockwise
(b) Anti clockwise
(c) Not any fixed direction
(d) None of these

(a) Clockwise

Explanation : It is evaluated by using Right Hand Thumb Rule.

Question.4.
On reversing the direction of the current in a wire, the magnetic fixed produced by it:

(a) Gets reversed in direction
(b) Increase in strength
(c) Decreases in strength
(d) Remains unchanged in strength and direction

(a) Gets reversed in direction

Explanation : When direction of current change, then direction of magnetic field produced changes accordingly.

Chapter 13: Magnetic Effects of Electric Current​

Case Study Question 06

Read the following and answer the following questions:

A magnet must exert an equal and opposite force on a current carrying conductor. We know that current is due to the charge in motion. Thus, it is evident that a charge moving in a magnetic field experiences a force. If the direction of motion is perpendicular to the direction of the magnetic field, the magnitude of force experienced depends upon the charge, velocity, and strength of the magnetic field. Fleming’s left-hand rule gives the direction of the magnetic force.Case_magnetic_07

Question.1.
If a charged particle is moving along a magnetic field line, the magnetic force on the particle is:

(a) along with its velocity.
(b) opposite to its velocity.
(c) perpendicular to its velocity.
(d) zero.

(d) zero

Question.2.
An electron is travelling horizontally towards the east. A magnetic field in the vertically downward direction will exert a force in:

(a) East
(b) West
(c) North
(d) South

(d) South

Question.3.
A uniform magnetic field exists from left to right on a surface. An electron and proton moving in the directions as shown in the figure will experience:Case_magnetic_08

(a) Forces both pointing into the plane of the surface.
(b) Forces both pointing out of the plane of the surface.
(c) The electron will experience into the plane and proton out of the plane.
(d) The electron will experience opposite to and proton along the direction of the uniform magnetic field.

(a) Forces both pointing into the plane of the surface

Question.4.
Magnetic field exerts no force on:

(a) a stationary electric charge.
(b) a magnet.
(c) an electric charge moving perpendicular to its direction.
(d) an unmagnetized iron bar.

(a) a stationary electric charge

Question.5.
In Fleming’s left-hand rule, the thumb’s direction shows the:

(a) current
(b) field
(c) motion
(d) charge

(c) motion

Chapter 13: Magnetic Effects of Electric Current​

Case Study Question 07

Read the following and answer the following questions:

The space surrounding a magnet in which magnetic force is exerted, is called a magnetic field. The direction of magnetic field lines at a place can be determined by using a compass needle. A compass needle placed near a magnet gets deflected due to the magnetic force exerted by the magnet. The north end of the needle of the compass indicates the direction of magnetic field at the point where it is placed. When the magnet shown in the diagram below is moving towards the coil, the galvanometer gives a reading to the right.Case_magnetic_09

Question.1.
The direction of induced current is given by:

(a) Right hand thumb rule
(b) Fleming’s right hand rule
(c) Fleming’s left hand rule
(d) Maxwell’s rule

(b) Fleming’s right hand rule

Question.2.
What is the condition of electromagnetic induction?

(a) There must be a relative motion between the coil of wire and galvanometer.
(b) There must be a relative motion between the galvanometer and a magnet.
(c) There must be a relative motion between galvanometer and generator.
(d) There must be a relative motion between the coil of wire and a magnet.

(d) There must be a relative motion between the coil of wire and a magnet.

Question.3.
A student writes a few statements after studying the principles of electromagnetism and working of electric motor:

(I) Fleming’s left hand rule is used to make electromagnet.
(II) Fleming’s left hand rule is used in electric motor.
(III) Fleming’s right hand rule is used in electric motor.
(IV) Right hand thumb rule is used in electric motor.

Choose the correct statement(s) from the following:

(a) Only (I)
(b) Only (II)
(c) (I) and (III)
(d) (II), (III) and (IV)

(b) Only (II)

Question.4.
When the magnet is moved away from the coil, it is observed that:

(a) the galvanometer needle deflects to the left
(b) the galvanometer needle deflects to the right
(c) the galvanometer needle first deflects to the left and then tothe right
(d) the galvanometer needle first deflects to the right and then to the left.

(a) the galvanometer needle deflects to the left.

Question.5.
The induced current is highest when:

(a) direction of magnetic field is parallel to the direction of motion of coil.
(b) direction of magnetic field is opposite to the direction of motion of coil.
(c) direction of magnetic field is perpendicular to the direction of motion of coil.
(d) direction of magnetic field is in straight line to the direction of motion of coil.

(c) direction of magnetic field is perpendicular to the direction of motion of coil.

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