CBSE Class 10 Science Magnetic Effects of Electric Current Assignment Set 04

Assertion and Reason Type Questions

Direction – In each of the following questions, a statement of Assertion is given by the corresponding statement of Reason. Of the statements, mark the correct answer as
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If Assertion is false, but Reason is true.
(e) If Assertion and Reason both are false.

ASSERTION AND REASON

Question. Assertion: A current-carrying conductor experiences a force in a magnetic field.
Reason: The force acting on a current-carrying conductor in a magnetic field is due to interaction between magnetic field produced by the current-carrying conductor and external magnetic field in which the conductor is placed.

Answer: A

Question. Assertion: Electric Motor converts Electric Energy into mechanical Energy.
Reason: Electric motor is based on the principle of Flemings right-hand rule.

Answer: C

Question. Assertion: Magnetic field lines do not intersect each other.
Reason: There cannot to two direction of the magnetic field at a point.

Answer: A

Short Answer Type Questions

Question. Why and when does a current carrying conductor kept in a magnetic field experience force? List the factors on which direction of this force depends?
Answer: The drifting of free electrons of a conductor in a definite direction causes the current to flow through it. When such conductor is placed in a uniform magnetic field, each drifted electron of a conductor experience a magnetic force. This force is collectively experience by a conductor as a whole. Hence a current carrying conductor kept in a magnetic field experience a force. The direction of magnetic force depends on
(i) direction of current through the conductor, and
(ii) direction of magnetic field.

Question. What are magnetic field lines? Justify the following statements
(a) Two magnetic field lines never intersect each other.
(b) Magnetic field lines are closed curves.
Answer: Magnetic field lines: It is defined as the path along which the unit North pole (imaginary) tends to move in a magnetic field if free to do so.
(a) The magnetic lines of force do not intersect (or cross) one another. If they do so then at the point of intersection, two tangents can be drawn at that point which indicates that there will be two different directions of the same magnetic which field, i.e. the compass needle points in two different directions which is not possible.
(b) Magnetic field lines are closed continuous curves. They diverge from the north pole of a bar magnet and converge its south pole. Inside the magnet they move from south pole to north pole.

Question. What is meant by solenoid? How does a current carrying solenoid behave? Give its main use.
Answer: Solenoid: A coil of many circular turns of insulated copper wire wound on a cylindrical insulating body (i.e., cardboard etc.) such that its length is greater than its diameter is called solenoid.

When current is flowing through the solenoid, the magnetic field line pattern resembles exactly with those of a bar magnet with the fixed polarity, i.e. North and South pole at its ends and it acquires the directive and attractive properties similar to bar magnet. Hence, the current carrying solenoid behave as a bar magnet.
Use of current carrying solenoid: It is used to form a temporary magnet called electromagnet as well as permanent magnet.

Long Answer Type Questions

Question. a)Describe an activity to demonstrate the pattern of magnetic field lines around a straight conductor carrying current.
(b) State the rule to find the direction of magnetic field associated with a current carrying conductor.
(c) What is the shape of a current carrying conductor whose magnetic field pattern resembles that of a bar-magnet ?
Answer: (a) Aim : To study the magnetic field due to a straight current carrying conductor.
Apparatus Required : A thick conducting wire, battery, rheostat, magnetic needle, ammeter (0-5 A), key, a cardboard, a stand to hold the wire, iron filings and sprinkler of iron filings.
Procedure :
1. Attach the thick wire through a hole at the middle of the cardboard and clamp it in a stand.
2. Attach the ends of the wire through a key, variable resistor and an ammeter on either side of a battery and hold it vertically and perpendicularly to the board.
3. Spread the iron filings uniformly on the cardboard and place the magnetic needle on the board.
4. Close the key and tap the cardboard slightly and observe the orientation of iron filings.

Observation :
1. Just on closing the key, the iron filings are aligned in the pattern of concentric circles around the wire.

Conclusion :
1. Current carrying conductor is a source of magnetic field.
2. The magnetic field is in the form of concentric circles whose centre lies on the wire.

(b) Right-Hand Thumb Rule. This rule is used to find the direction of magnetic field due to a straight current carrying wire.

It states that if we hold the current carrying-conductor in the right hand in such a way that the thumb is stretched along the direction of current, then the curly finger around the conductor represent the direction of magnetic field produced by it. This is known as right-hand thumb rule.
Direction of Field Lines due to current carrying straight conductor is as shown in figure.

(c) Solenoid.