CHAPTER-13
MAGNETIC EFFECTS OF ELECTRIC CURRENT
Key Points and Concepts
Right Hand Thumb Rule : Hold the wire
carrying current in your right hand, such that
the thumb indicates the direction of current, then the folded fingers will indicate the presence
of magnetic field (lines) surrounding the wire.
 Faraday’s Law : The rate at which the magnetic flux linked with a coil changes, produces the induced emf or
current. More the rate, more the current and vice-versa.
I=
‘ Electric Motor and Generator:
e
Chance in flux
=
R Resistance × Time
Current rating
‘ No. of lamps =Current through one lamp
• Important Graphs and Diagrams
 Uniform Magnetic Field
 Magnetic Lines around two magnets
 Magnetic Lines around a bar magnet
 Magnetic Lines due to a current carrying loop
 Magnetic field in a solenoid
 Magnetic Lanes produced around a current carrying conductor.
 Common Domestic CircuIt
ASSIGNMENT -04
Short answer type questions (2 marks each):
1. a) Two magnets are lying side by side as shown below. Draw magnetic field lines between
Poles P and Q.
b) What does the degree of closeness of magnetic field lines new-the Pole signifies?
2. A Compass needle is placed new- a current carrying wire. State your observation for the following cases and
give reason:a) Magnitude of electric current in the wire is increased.
b) The compass needle is displaced away from the wire.
3. How is the strength of a magnetic field new- a straight current carrying conductor:
a) Related to the strength of current in the conductor
b) Is affected by changing the direction of flow of current in the conductor?
4. List two major differences between an electric motor and a generator.
Short answer type questions (3 marks each)
1. 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.
2. For the current carrying solenoid as shown below draw magnetic field lines and giving reason explain that out
of three regions A, B and C, at which point the field strength is maximum and at which point it is minimum?
III. Long answer type questions (5 marks each)
I. a) Describe an activity to demonstrate the pattern of magnetic field lines around a straight current carrying
conductor.
b) State the rule to find the direction of magnetic field around the current carrying conductor.
c) What is the shape of current carrying conductor whose magnetic field pattern resembles that of a bar magnet?
2. a) Explain why there are two separate circuits, one for high power rating appliances another for low power
rating appliances
b) A domestic circuit has 5 A fuse. How many bulbs of rating 100W, 220 V can be safe4 used in the circuit?
3. (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:
(i) Armature _________________________________________________
(ii) Brushes _________________________________________________
(iii) Split ring _______________________________________________
Draw a sketch of the pattern of field lines due to a:
(a) Current flowing into a circular coil.
(b) Solenoid carrying current.
ASSIGNMENT -05
PRACTICAL BASED ASSIGNMENT (2 MARKS EACH)
Observe the following incomplete ray diagram of an object where the image A’B’ is formed after refraction from
a convex lens.
On the basis of above information fill in the blanks:
a) The position of object AB would have been _______________
b) Size of the object would have been ________than the size of image.
2. In a given ammeter, a student sees that needle indicates 17 divisions in ammeter while performing an
experiment to verify Ohm’s law. if ammeter has 10 divisions between 0 and 0.5 A, then what is the value
corresponding to 17 divisions?
3. Draw a path of light ray passing through a prism. Label angle of incidence and angle of deviation in the ray
diagram.
4. In a voltmeter there are 20 divisions between the 0 mark and 0.5 V mark Calculate the least count of the
voltmeter.
5. A student focussed the sun rays using an optical device ‘X’ on a screen S as shown.
What conclusion can be drawn based on this about device X?
6. The current flowing through a conductor and the potential difference across its ends are as per the readings of
ammeter and voltmeter shown below. The resistance of the conductor would be
7. If two resistors of value R are connected in series and then in parallel , what is the difference in equivalent
resistance in both cases?
the
8. If the applied voltage (V) across both the resistors R1 and R2 is same but R1> R2 then what would be true about
ammeter readings A1 and A2?
The correct voltmeter and ammeter connections in an experiment to find the equivalent resistance when two
resistors are connected in parallel is shown in____.
10. The values of current (I) flowing through a given resistor of resistance (R) for the corresponding values :f
potential difference (V) across the resistor are as given below:
Plot a graph between current (I) and potential difference (V) and determine the resistance (R) of the resistor.
11. (a) Should the resistance of ammeter be low or high? Give reason.
(b) Out of the two wires X and Y shown below which one has greater resistance?
Justify your answer.