CBSE Class 10 Physics Magnetic Effect of Electric Current Worksheet Set A

Question. Name the device which is used to draw magnetic field lines.
Answer: Compass needle.

Question. A current carrying straight wire held perpendicular to the plane of paper and current passes through this conductor in the vertically upward direction. What is the direction of magnetic field produced around it?
Answer: According to right-hand thumb rule, the direction of magnetic field produced around the given conductor is anticlockwise.

Question. The wire in the figure below is being moved downwards through the magnetic field, so as to produce induced current.
What would be the effect of :
(a) moving the wire at a higher speed?
(b) moving the wire upwards rather than downwards?
(c) using a stronger magnet?
(d) holding the wire still in the magnetic field? 

Answer: (a) The induced current increases at a higher speed.
(b) The induced current is reversed.
(b) The induced current increases.
(d) The induced current is zero.

Question. Answer the following questions:
(a) Name and state the rule to determine the polarity of the two faces of a current carrying circular loop.
(b) State Fleming’s Left Hand Rule.
Answer: (a) Clock face rule is used to determine the polarity of the two faces of a current carrying circular loop. According to this rule, “If the current around the face of circular wire flows in the clockwise direction, then that face of the circular wire will be south pole (S-Pole) and if the current around the face of circular wire flows in the anticlockwise direction, then that face of the circular wire will be north pole (N-Pole).”
(b) According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular to each other. If the first finger points in the
direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.

Question. When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
Answer: The force experienced by a current-carrying conductor placed in a magnetic field is largest when the current-carrying conductor is placed perpendicular to the direction of magnetic field.

Question. Imagine that you are setting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field ?
Answer: As the electron beam moves from back wall towards the front wall, it implies that the current is travelling from front to back wall. Deflection towards right side indicate the direction of the force. Thus by using Fleming's left hand rule, the direction of the magnetic field would be from of the room towards the floor, i.e., from top to bottom or downwards. 

Question. Answer the following questions:
(a) What is the principle of an electric motor? 
(b) What is the role of a split ring in an electric motor?
(c) Define magnetism.
Answer: (a) Electric motor works on the principle that ‘when a rectangular coil is placed in a magnetic field and current is passed through it, a force acts on the coil which rotates it
continuously. Thus, when the coil rotates, the shaft attached to it also rotates converting the electrical energy supplied to the motor to the mechanical energy of rotation.
(b) In an electric motor, after every half rotation the direction of coil gets reversed due to change in orientation of the magnetic field. To ensure a continuous rotation; a split ring is
attached to the coil so that the polarity of the coil changes after every half rotation. This changes the direction of current and thus the armature keeps on rotating continuously.
(c) The property by virtue of which a magnet attracts certain metals such as iron, cobalt, nickel etc., is termed as magnetism.

Question. State Fleming’s right hand rule.
Answer: It states that, “Stretch your right hand in such a way that the first finger, the central finger and the thumb are mutually perpendicular to each other. If the first finger points along the direction of magnetic field and the thumb points along the direction of motion of the conductor, then the direction of induced current is given by the direction of the central finger.” This rule is also called dynamo rule. 

Question. Answer the following questions:
(a) Define electromagnetic induction.
(b) What is a permanent magnet? Give one use of it.
(c) Define a compass.
Answer: (a) The production of electricity from magnetism is called electromagnetic induction.
(b) A permanent magnet is a magnet made from steel such that once magnetized, it does not lose its magnetism easily.
(c) A compass is a device used to show magnetic field direction at a point. It consists of a tiny pivoted magnet usually in the form of a pointer which can turn freely in the horizontal plane.

Question. What is a solenoid ? Draw the pattern of magnetic field lines of (i) a current carrying solenoid and (ii) a bar magnet. List two distinguishing features between the two fields.
Answer: Solenoid is a long cylindrical coil of wire consisting of a large number of turns bound together very tightly. 

Distinguishing features are as follows :
1. Magnetic field outside the solenoid is negligible as compared to the bar magnet.
2. Magnetic field of solenoid can be varied as per our requirement just by changing current or core of solenoid but in bar magnet it is fixed.

Question. In the diagram XY is a straight conductor carrying current in the direction marked by the arrow. The conductor is held vertically by passing it through a horizontal cardboard sheet. Draw three magnetic lines of force on the board and mark the direction of magnetic field in your diagram. State two factors on which magnitude of magnetic field at a point, depends.
Answer: The magnetic lines of force due to current in the straight conductor XY are shown in figure given alongside. The arrows on the magnetic lines of force show the direction of magnetic field.
The magnitude of magnetic field at a point depends on :
(i) The strength of current in the conductor, and
(ii) The distance of point from the conductor. 

Question. Which way does the wire carrying current in the given figure tend to move ? 

Answer: Applying Fleming's left hand rule, the wire carrying current tends to move upwards .

Question. Answer the following questions:
(a) What do you mean by ‘magnetic field’ of a magnet?
(b) What are magnetic field lines? List two characteristic properties of these lines.
Answer: (a) The space or region around a magnet in which the force of attraction or repulsion due to the magnet can be detected is called the magnetic field.
(b) The lines drawn in a magnetic field along which north magnetic pole moves, are called magnetic field lines.
The characteristic properties of magnetic field lines are :
(i) The magnetic lines originate from north pole and ends at south pole.
(ii) The magnetic lines do not intersect each other.

Question. Sketch the lines of force of the magnetic field of a solenoid. How does its field compare with that of a bar magnet ?
Answer: The magnetic field of a solenoid is very similar to that of a bar magnet. this is shown in figure (a) and (b) respectively, which shows the lines of force of the magnetic field of a current carrying solenoid and a bar magnet. 124

Question. State the condition in each case of the magnitude of force on a current carrying conductor placed in a magnetic field to be (a) zero and (b) maximum.
Answer: (a) The magnitude of force acting on a current carrying conductor placed in a magnetic field will be zero, when the current carrying conductor is in the direction of magnetic field.
(b) The magnitude of force acting on a current carrying conductor placed in a magnetic field will be maximum, when the current carrying conductor is normal (perpendicular) to the magnetic field.

Question. How will you decide whether the magnetic field at a point is due to some current carrying conductor or due to earth?
Answer: Place a compass needle at the given point. If it stays in the north-south direction, then the magnetic field is due to earth. If the needle points along any direction other than north-south direction, then the field is due to some current carrying conductor.

Question. Two magnets are lying side by side as shown below. Draw magnetic field lines between poles P and Q. 

Answer: Magnetic field lines are shown below: 

Creating Based Questions :

Question. Using the following informations form a pathway that defines the working of the electric motor. And also include informations that are not mentioned below to complete it.
Battery, Horse-shoe magnet, vertical position, Commutator, rectangle coil, Magnetic force, horizontal position.
Answer: Rectangle coil is placed between horse-shoe magnet → Coil is connected to the battery through brush and commutator → The current flow through the coil which is placed between magnetic field → Rectangle coil rotates from the horizontal position → The current stops flowing when the coil attains vertical position because the brush and the
commutator ring will not be in connection → Though the coil keeps rotating because of the momentum from the earlier rotation → Now the coil attains horizontal position Coil again starts to rotate With the → help of Fleming’s left-hand rule, the direction of the rotation of the coil is determined.

Question. Using the following informations form a pathway to determine the direction of the motor in an electric motor. And also include informations that are not mentioned below to complete it. Motion of the conductor, Direction of current, three fingers, Magnetic field, Index finger, motion of the conductor.
Answer: Three fingers → In left-hand → Index finger → Middle finger → Thumb → At right angle → Middle finger represents the direction of the current → Index finger represents the direction of the magnetic field → Thumb represents the direction of the motion of the conductor → Used to define the direction of the motion of the conductor in electric motor → Also known as motor rule.

Question. Using the following informations form a pathway that defines the working of the electric motor. And also include informations that are not mentioned below to complete it. Battery, Horse-shoe magnet, vertical position, Commutator, rectangle coil, Magnetic force, horizontal position.
Answer: Rectangle coil is placed between horse-shoe magnet → Coil is connected to the battery through brush and commutator → The current flows through the coil which is placed between magnetic field → Rectangle coil rotates from the horizontal position → The current stops flowing when the coil attains vertical position because the brush and the commutator ring will not be in → connection Though the coil keeps rotating because of the momentum from the earlier rotation → Now the coil attains horizontal position → Coil again starts to rotate → With the help of Fleming's left-hand rule, the direction of the rotation of the coil is determined.

Question. Suggest a method by which Simran could determine the direction of the magnetic field in a generator.
Answer: Fleming’s right-hand rule is generally used for determining the direction of the current, magnetic field and the motion of the conductor in a generator. Here, one can determine the
directions by placing the thumb, forefinger and the middle finger of the right-hand perpendicular to each other. The thumbrepresents the motion of the conductor, the forefinger and the
middle finger represent the direction of the magnetic field and the induced current respectively.

Question. Using the following informations form an instruction to draw magnetic lines. And also include informations that are not mentioned below to complete it.
Magnetic compass, repel, board, Bar magnet, Needle, attract, Merge, Emerge.
Answer: Place a board → Place a bar magnet in the middle → Mark the boundary of the bar magnet → Place the magnetic compass near the North Pole of the bar magnet → North side of the needle points away from the north side of the magnet → Same poles repel each other → different poles attract each other → Now place the pin in the direction the needle points → Move the compass to new position where south pole points the previous position of the north → pole Repeat the → procedure Magnetic lines emerge at north pole → Magnetic lines merge at south pole → This forms concentric magnetic lines around bar magnet.

Question. What would be the inference made by Prashant about the magnetic strength when current passed through a circular coil produces a magnetic field?
Answer: Magnetic field lines form in concentric circles around a cylindrical current-carrying conductor, such as a length of wire. The strength of the magnetic field at the centre of a circular coil carrying current is inversely proportional to the radius of the circular coil i.e., the field strength reduces as the radius of the coil increases.

Miscellaneous Based Questions :

Question. List three sources of magnetic fields.
Answer: Three methods of producing magnetic fields are as follows:
(a) By permanent magnet.
(b) By electromagnet
(c) By current carrying conductors.

Question. What are the factors affecting the strength of an electromagnet ?
Answer: Factors affecting the strength of an electromagnet : The strength of an electromagnet depends on :
1. The number of turns in the coil : If we increase the number of turns in the coil, the strength of electromagnet increases.
2. The current flowing in the coil : If the current in the coil is increased, the strength of electromagnet increases.
3. The length of air gap between its poles : If we reduce the length of air gap between the pole of an electromagnet, then its strength increases.

Question. (a) State Fleming's left hand rule.
(b) Write the principle of working of an electric motor.
(c) Explain the function of following parts of an electric motor:
(d) Armature (ii) Brushes (iii) Split ring.
Answer: (a) According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
(b) Principle of electric motor : When a coil carrying current is placed in a magnetic field, it will experience a force. As a result of this force, the coil begins to rotate.
(c) (i) Armature: It creates a magnetic field and the second role is to generate electromotive force.
(ii) Brushes: Carbon brushes are used to make contract with the rotating rings of the commutator and through them to supply current to the coil.
(iii) Split ring: Split rings are used to reverse the direction of current flowing through the coil every time the coil just passes the vertical position during a revolution.

Question. Explain different ways to induce current in a coil.
Answer: The different ways to induce current in a coil are :
1. By moving the coil in a magnetic field.
2. By changing the magnetic field around the coil.

Question. The magnetic field in a given region is uniform. Draw a diagram to represent it. 
Answer: 

Question. Draw magnetic field lines around a bar magnet.
Answer: 

Question. Write the factors on which the strength of magnetic field produced by a current carrying solenoid depends ?
Answer: The strength of magnetic field produced by a current carrying solenoid depends on :
1. The number of turns in the solenoid : Larger the number of turns in the solenoid, greater will be the magnetism produced.
2. The strength of current in the solenoid : Larger the current passed through solenoid, stronger will be the magnetism produced.
3. The nature of core material used in making solenoid : The use of soft iron rod as core in a solenoid produces the stronger magnetism.

Question. Name some devices in which electric motors are used. 
Answer: Electric fan, mixer grinder, tape recorder, CD player, hard disk drive, washing machine, cooler, toy car, vacuum cleaner, etc., are some devices in which electric motor is used.

Question. How will the direction of force be changed, if the current is reversed in the conductor placed in a magnetic field ?
Answer: The direction of the force will be reversed.

Question. Complete the following sentences :
(a) A current carrying solenoid behaves like a …………
(b) A current or a moving charge produces a ……………… around it.
Answer: (a) bar magnet (b) magnetic field.

Question. Draw the pattern of magnetic field lines around a current carrying straight conductor. How does the strength of the magnetic field produce change :
(a) with the distance from the conductor ?
(b) with an increase in current in a conductor ?
Answer: (a) The strength of a magnetic field is inversely proportional to the square of the distance from the conductor i.e., strength of an electric field decreases with increase in distance.
(b) The strength of the magnetic field is directly proportional to the current passing in the wire i.e., strength of the magnetic field increases with the increase in current. 161

Question. List the properties of magnetic lines of force.
Answer: Properties of magnetic field lines:
(a) Magnetic field lines follow the direction from the North Pole to the South Pole.
(b) Magnetic field lines always form closed circular loops.
(c) Magnetic field lines do not cross one another.
(d) Closer the field lines; stronger is the magnetic field and viceversa.
(e) Magnetic field lines are closer near the poles; which shows greater strength of magnetic field near the poles.