>

## Solutions of Magnetic Effects of Electric Current Lakhmir Singh Manjit Kaur  VSAQ, LAQ and MCQ Pg No. 73 Class 10 Physics 1. State any two properties of magnetic field lines.

→ The two properties of magnetic field
Lines are:
pole of the magnet and ends at the south pole of the very same.
(b) the closer the field lines will be
the stronger will be the magnetic

field.

2. What are the two ways in which you can trace the magnetic field pattern of a bar magnet?

→ The two ways are :
(a) with the help of a compass, as it always indicate the north pole.
(b) it can be traced by sprinkling iron dust.

3. You are given the magnetic field pattern of a magnet. How will you find out from it where the magnetic field is the strongest ?

→ As we know, the magnetic field is Stronger where the field line is Closest. So the area with the Closest field line in the given Pattern have the strongest Magnetic field.

4. State whether the following statement is true or false :
The axis of earth's imaginary magnet and the geographical axis coincide with each other.

→ False
The two axis do not coincide with each other as they are separated by an angle of about 17 degree.

5. Why does a compass needle get deflected when brought near a bar magnet?

→ A compass needle is a small bar magnet. when it is brought near to another bar magnet their field lines interact with each other.
Hence, the compass needle shows deflection.

6. Where do the manufacturers use a magnetic strip in the refrigerator? Why is this magnetic strip used?

→ To keep the door closed properly manufacturers use a strip of magnets at the doors of refrigerators.

7. Fill in the following blanks with suitable words :
(a) Magnetic field lines leave the..........pole of a bar magnet and enter at its........pole.
(b) The earth's magnetic field is rather like that of a ......... magnet with its........pole in the northern hemisphere.

→ (a) North, south (magnetic field lines begins with north pole and end at the south pole.)
(b) bar, south.

8. Draw a diagram to show the magnetic field lines around a bar magnet The field lines begins with north pole and ends at south pole.

9. What is a magnetic field? How can the direction of magnetic field lines at a place be determined?

→ The area in which the force of magnet is exerted is called magnetic field line to determine the magnetic field line direction you to place a compass on a plane the direction of the needle of a compass shows the north pole, and so will be the direction of the magnetic field line which begins with the north pole and end at south pole.

10. Explain why, two magnetic field lines do not intersect each other.

→ As a matter of fact the resultant of forces at north pole can only be in one direction. But if magnetic field lines intersect each other then the north pole will show resultant forces in two direction, which is not possible.

11. When an electric current is passed through any wire, a magnetic field is produced around it. Then why an electric iron connecting cable does not attract nearby iron objects when electric current is switched on through it?

→ This is because, the field produced is very weak.

12A. Define magnetic field lines. Describe an activity to draw a magnetic field line outside a bar magnet from one pole to another pole.

→ A magnetic field lines are lines which are drawn around the magnet and which always starts with the north pole and ending at the south pole.
Activity:
> to draw a magnetic field line around the bar magnet.
> take a bar magnet and a compass and place them on a plane over a hard sheet.
> the boundary of the marker should be marked.
> Place the compass near the north pole of the magnet. The south pole of the needle points towards the north pole of the magnet. The north pole of the compass is directed away from the north pole of the magnet.

> mark the both end of the needle.
> now move the needle to a new position such that the previously occupied north position should now occupy the south position and vice versa.
> continue this process till you the south pole of the bar magnet.
> now by joining all the points by a curve will represent the magnetic field line.

12B. Explain why, a freely suspended magnet always points in the north-south direction.

→ The earth itself act as a magnet .and its geographical north is in south pole and the geographical south in north pole .so a freely suspended magnet always points in north-south direction.

Multiple Choice Questions (MCQs)-Pg-73

13. A strong bar magnet is placed vertically above a horizontal wooden board. The magnetic lines of force will be:
A. only in horizontal plane around the magnet
B. only in vertical plane around the magnet
C. in horizontal as well as in vertical planes around the magnet
D. in all the planes around the magnet

→ This is because magnet exert force in every direction.

14. The magnetic field lines produced by a bar magnet :
A. originate from the south pole and end at its north pole
B. originate from the north pole and end at its east pole
C. originate from the north pole and end at its south pole
D. originate from the south pole and end at its west pole

→ The magnetic field line always originates from the north pole and ends at south pole.

15. Which of the following is not attracted by a magnet ?
A. steel
B. cobalt
C. brass
D. nickel

→ Because brass is an alloy.

16. The magnetic field lines :
A. intersect at right angles to one another
B. intersect at an angle of 45° to each other
C. do not cross one another
D. cross at an angle of 60° to one another

→ Magnetic field line never intersect each other.

17. The north pole of earth's magnet is in the:
A. geographical south
B. geographical east
C. geographical west
D. geographical north

→ Geographical south is in the north pole.

18. The axis of earth's magnetic field is inclined with the geographical axis at an angle of about:
A. 5°
B. 15°
C. 25°
D. 35°

→ 15°

19. The shape of the earth's magnetic field resembles that of an imaginary:
A. U-shaped magnet
B. Straight conductor carrying current
C. Current-carrying circular coil
D. Bar magnet

→ Bar magnet.

20. A magnet attracts:
A. plastics
B. any metal
C. aluminium
D. iron and steel

→ Iron and steel shows magnetic behaviour.

21. A plotting compass is placed near the south pole of a bar magnet. The pointer of plotting compass will :
A. point away from the south pole
B. point parallel to the south pole
C. point towards the south pole
D. point at right angles to the south pole

→ The plotting compass is placed near the south pole of a bar magnet. The pointer of plotting compass will point at right angles to the south pole.

22. The metallic pointer of a plotting compass gets deflected only when it is placed near a bar magnet because the pointer has :
A. electromagnetism
B. permanent magnetism
C. induced magnetism
D. ferromagnetism

→ The metallic pointer of a plotting compass get deflected only when it is placed near a bar magnet because the pointer has permanent magnetism.

23. Which of the following statements is incorrect regarding magnetic field lines ?
A. The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points.
B. Magnetic field lines are closed curves
C. If magnetic field lines are parallel and equidistant, they represent zero field strength
D. Relative strength of magnetic field is shown by the degree of closeness of the field lines.

→ The strength of field is zero, when the magnetic field lines are equidistance and parallel.

Questions Based on High Order Thinking Skills (HOTS)-Pg-74

24. Copy the figure given below which shows a plotting compass and a magnet. Label the N pole of the magnet and draw the field line on which the compass lies.  As the needle of the compass is tending to move toward the other end of the bar magnet, so the nearer end will show the north pole and the other end will show the south pole.

25A. The diagram shows a bar magnet surrounded by four plotting compasses. Copy the diagram and mark in it direction of the compass needle for each of the cases B, C and D. → Arrows shows the direction due to the deflection.
As the 25B. Which is the north pole, X or Y ? → As we see in the figure, the pointer is pointing away from the magnet. It means X is the NORTH POLE.

26. The three diagrams in the following figure shows the lines of force (field lines) between the poles of two magnets. Identify the poles A, B, C, D, E and F. → A=N, B=N, C=S, D=S, E=N, and F=S.
The field lines originate from the north pole and end at the south pole.

27. The figure given below shows the magnetic field between two magnets: (i) Copy the diagram and label the other poles of the magnets.
(ii) Which is the weaker magnet?

→ (i) S-N, N-S The field line always emits form the north pole and ends at the south pole.
(ii) Magnet 2 is the weaker magnet.
It has small magnetic field.

1. Which effect of current can be utilised in detecting a current-carrying wire cancelled in a wall?

→ Magnetic effect of a current can be utilised in detecting a current carrying wire cancelled in a wall.

2. What conclusion do you get from the observation that a current-carrying wire deflects a compass needle placed near it?

→ By the deflection of a compass needle, when placed near a current carrying wire gives a conclusion that there is a magnetic field produced around the wire.

3. Name the scientist who discovered the magnetic effect of current.

→ Oersted, was the scientist who first discovered the magnetic effect of current.

4. State qualitatively the effect of inserting an iron core into a current-carrying solenoid.

→ The magnetic field become very strong when the iron core is inserted into a current carrying conductor.

5. Name the rule for finding the direction of magnetic field produced by a straight current-carrying conductor.

→ The rule for finding the direction of magnetic field produced by a straight current carrying conductor was given by Maxwell’s right hand thumb rule.

6. State the form of magnetic field lines around a straight current--++carrying conductor.

→ A concentric circle is formed around a straight current carrying conductor and its centre lies in the conductor.

7. What is the other name of Maxwell’s right-hand thumb rule?

→ Maxwell’s corkscrew rule is the other name for the Maxwell’s right-hand thumb rule.

8. State whether the following statement is true or false:
The magnetic field inside a long circular coil carrying current will be parallel straight lines.

→ True, Inside a long circular coil carrying current the magnetic field lines are always parallel with each other.

9. What is the shape of current-carrying conductor whose magnetic field pattern resembles that of a bar magnet?

→ A current carrying conductor is of solenoid shape whose magnetic field pattern seems to that of the bar magnet.

10. State three ways in which the strength of an electromagnet can be increased.

→ The three ways are :-
(1) By increasing the number of turns in the coil.
(2) Increase the current flow in the coil.
(3) The air gaps between the poles should must be reduced.

11. Fill in the following blanks with suitable words:
(a) The lines of _____ round a straight-carrying conductor are in the shape of _____
(b) For a current-carrying solenoid, the magnetic field is like that of a _____
(d) The magnetic effect of a coil can be increased by increasing the number of _____, increasing the _____ or inserting an _____ core.
(e) If a coil is viewed from one end and the current flows in an anticlockwise direction, then this end is a _____ pole.
(f) If a coil is viewed from one end, and the current flows in a clockwise direction, then this end is a _____ pole.