1) When current passes through a wire, it produces a magnetic field that can be detected using a compass. The compass needle will deflect due to the magnetic field produced by the current-carrying wire. 2) The direction of the magnetic field produced around a current-carrying straight wire can be determined using the right-hand rule. Reversing the current reverses the direction of the magnetic field. 3) A current-carrying circular loop produces concentric circular magnetic field lines, with the field lines becoming straight and perpendicular to the plane of the coil at the center.

1. Magnetic Effects
of Current
Class 10: CBSE (2020)

2. LET’S RELATE MAGNET AND CURRENT
CONDUCTING WIRE MAGNET
August 5, 2020deepsha 2

3. ACTIVITY 13.1
Procedure:Place a copper wire near a compass and switch on the
current.
Observation: Compass needle deflects when electricity passes through
the copper wire.
Explanation:
Whenever there is a change in the current, it produces an electric field. In
normal usage, a compass detects the magnetic field of the earth. When
we bring the compass near a wire and pass current, an artificial magnetic
field produces. This artificial magnetic field deflects the compass.
Note: This is one of the fundamental property of the current. It was
discovered accidently by Oersted using the same experiment. This
discovery led to the invention of many devices like the radio, TV, etc. So,
in his honor, we call the unit of a strength of magnetic field
as Oersted ‘O‘.
Conclusion: This phenomenon shows the relationship between the
current flowing through a wire and its magnetic effect. It shows that a
current produces magnetic filed which deflect the compass.
• Compass needle is deflected on passing an electric current through a
metallic conductor
• Electric current carrying wire behaves like a magnet. The deflected
needle proves that magnetic effect is produced by the current
August 5, 2020deepsha 3

4. Magnetic Field- Definition
• The magnetic field of magnet is the region surrounding a magnet
in which the force of the magnet can be detected
• It is a Vector quantity which means it has both magnitude and
direction.
• SI Unit – Tesla (T)
• Symbol- B
• The direction of magnetic field is taken to be the direction in which
a north pole of the compass needle moves inside it.
• Magnetic field exists near a bar magnet. August 5, 2020deepsha 4

5. MAGNETIC FIELD LINES
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6. Activity 13.2
Procedure: Throw/dust some iron filings near a bar
magnet.
Observation: Iron filings arrange themselves in a
fixed parabolic pattern.
Explanation: A bar magnet attracts iron particles.
This force of attraction differs from place to place
near a magnet and forms a magnetic field of
characteristic shape. When we dust the iron filings,
iron particles arrange themselves in a fixed pattern
as per the nearby magnetic field.
Conclusion: A magnet has a magnetic field in its
surrounding which differ from place to place.
Iron fillings align
themselves along
the field
lines(fig.13.4)
August 5, 2020deepsha 6

7. PROPERTIES OF FIELD
LINES
• It represents a magnetic field.
• The magnetic field lines are directed from North pole of magnet towards the south
pole. ( inside the magnet lines are from south to north)
• Magnetic field lines are closed curves.they form a pattern of concentric circles.
• Relative strength of magnetic field lines is given by the degree of closeness of the
field lines.
• No two magnetic lines can ever intersect with each other . (WHY)
• Tangent to magnetic field line gives the direction of magnetic field at that point.
August 5, 2020deepsha 7

8. Activity 13.3
• Observation: The compass needle always remains in
one direction i.e. North pole of the needle always point
towards the south.
• Explanation: A magnet consists of two opposite poles:
the north and the south. A compass needle is also a small
bar magnet. It also has a north as well as a south pole.
North pole of a magnet attracts south pole only. So, when
we place the compass near a magnet, the north pole of
the compass aligns itself to the south pole of the magnet.
When we move the compass only the magnetic field
intensity changes; the direction of the pole remains the
same. As a result, we see the same direction in the
compass near a magnet.
• Conclusion: Here we see that poles of a magnet attract
the opposite poles only. This means the magnetic field
has a direction. For convention, we assume the magnetic
field emerges from the north and goes into the south. August 5, 2020deepsha 8

9. HC Oersted experiment we
can find the direction of magnetic field by
current carrying conductor
• .
Experiment to Demonstrate the Magnetic
Effect of Current
Make a simple electrical circuit by joining a long
straight wire with a battery and a plug. Now,
take a magnetic compass needle and place the
straight wire parallel to and over the compass
needle. Then switch on the circuit so that
current flows through the wire from south to
north directions. Now, you will found that the
north pole of compass needle gets deflected
towards the west. But, if the direction of current
in the wire is reversed then the north pole of the
compass needle gets deflected onwards the
east. The direction of deflection of magnetic
needle can be easily determined by SNOW
rule.
August 5, 2020deepsha 9

10. Oersted and his rule
Arrange the
circuit
August 5, 2020deepsha 10

11. ACTIVITY :13.4- Change the direction of current in a wire and see the deflection in the
compass.
Observation: When we reverse the direction of the current, compass needle also reverses its direction.
If current flows from north to south, the direction of the needle is east; similarly, if the direction of current
is reversed the direction of compass point towards west.
Explanation:
When we pass current into a wire, it produces a magnetic field. This field is perpendicular to the direction
of the current. So, if current flows from north to south, east becomes the north pole of the magnetic field.
In such a situation the south pole of magnet aligns with the north pole and see compass directing
towards the east.
Similarly, if we change the direction of the current by changing the terminals of the battery, the direction
of current reverses. This results in the production of a magnetic field in the opposite direction. As a result,
the compass also reverses its direction.
Conclusion: Magnetic filed is a vector quantity.
Note: We can use Right thumb rule to find the direction: Palm on the plane and movement of fingers in
the direction of the current gives thumb as North pole.
August 5, 2020deepsha 11

12. Right hand thumb rule
It was devised by Maxwell and this rule is also known as ' Maxwell's corkscrew rule ' This rule
is used to find the direction of magnetic field lines through a rod , Circular loop, Circular coil, and
Solenoid.
Hold a current carrying conductor in right hand , such that let the thumb points the towards the
direction of current. Then wrap the fingers around the conductor, and the finger points the direction of
the field lines of magnetic field. This is Right Hand Thumb rule.
August 5, 2020deepsha 12

13. Describe an activity to determine the direction of magnetic field produced by a current carrying straight
conductor. Also show that the direction of the magnetic field is reversed on reversing the direction of
current.
If the key in the arrangement as shown below is taken
out (the circuit is made open) and magnetic field lines are
drawn over the horizontal plane ABCD, the lines
are [NCERT Exemplar]
a) concentric circles
(b) elliptical in shape
(c) straight lines parallel to each other
(d) concentric circles near the point O but of elliptical
shapes as we go away from it
Answer:
(c) When the key is taken out (the circuit is made open),
no current flows through the wire, hence no magnetic
field exists due to the conductor.
The only magnetic field is due to Earth’s magnetic field
and are straight lines parallel to each other. The
horizontal component is directed from geographical
South to geographical North on the horizontal plane FIG 13.7
August 5, 2020deepsha 13

14. Factors on which magnetic field
produced by a current carrying straight
conductor depends
• Magnitude of current- B
• Direction of current : on changing direction of current ,the direction of field is
reversed
• Distance from the conductor - Magnetic field produced by the conductor
decreases as the distance from it increases.
August 5, 2020deepsha 14

15. Magnetic field lines of magnetic field
produced by Current carrying through
circular loop
• The magnetic field around a
straight current carrying conductor or
wire can be increased by bending the
wire into circular loop.
• Each small section of current
carrying wire contributes to magnetic
field lines. At the center
of circular wire, field lines become
straight and perpendicular to the plane
of coil.
CONTD…
August 5, 2020deepsha 15

16. NCERT Experiment ~
ACTIVITY 13.6
•At every point of current-carrying circular
conductor, the magnetic field is in the form of
concentric circles as represented above.
•The circles are concentric in nature with
increasing diameters as the move farther from the
current carrying wire.
•At the center of the circular loop, the circles
appear like straight lines.
•The magnetic field produced by a current-
carrying straight wire depends inversely on the
distance from it and directly on the current
passing through it.
The Right Hand Thumb Rule is applicable here
at every point of the current carrying conductor
August 5, 2020deepsha 16

17. Jack n jill “lets learn thumb rule”
• Jack n jill took a wire thin
• With THUMB holding I
(CURRENT) upwards
• Jack saw a cork and
curled his finger
• & jill came with the RHT
answer
August 5, 2020deepsha 17

18. Magnetic field lines of magnetic field
produced by Current carrying through
solenoid
• A coil with many circular close turns of insulated copper wire (like a
cylinder) is a solenoid.
• One end of such a solenoid behaves like the north pole and the
other as a south pole.
• Therefore magnetic field due to current in the solenoid is similar to a
bar magnet. The fields always emerge out of the North pole and
always merge into the South pole
• The magnetic field lines inside the solenoid are in the form of
parallel straight lines. So magnetic field is same at all points inside
the solenoid.
• The field inside the solenoid is uniform.
• The strong magnetic field inside the solenoid is so strong that it can
be used to magnetize a piece of soft iron when it is placed inside
the coil. The magnet formed like this is called a Electromagnet
FIG 13.10 Page 229
(ncert) August 5, 2020deepsha 18

19. Electromagnet and it’s strength
• Definition -The temporary magnet produced by electricity is called an electromagnet.
• Structure-Electromagnets are made out of a coil of wire tightly coiled around soft iron
connected to a circuit.
• Uses-Particle Accelerators
Amplifiers
Magnetic Separation
Electric Motors and Generators
MRI machines
Control Switches in Relays
Transportation
• Working principle- the strength of an electromagnet can be changed by changing the amount
of electric current that flows through it. Once the current stops the electromagnet
August 5, 2020deepsha 19

20. Flemings left hand rule and EMF
• Stretch the forefinger, the central finger and the thumb of your left hand
mutually perpendicular to each other . If the forefinger shows the direction
of magnetic field and the central finger that of current , then the thumb
will point towards the direction of motion or the force acting on the
conductor.
• EMF- EMF is defined as the work done on a unit charge
• It is represented by E
• It was given by James Maxwell.
August 5, 2020deepsha 20

21. Fun filled fleming left “rule”
• Fleming called FBI to check current in his left hand
August 5, 2020deepsha 21
Named after British engineer John Ambrose Fleming, who invented it

22. FACTORS ON WHICH FORCE DEPENDS
• Strength of magnetic field (B)~ directly proportional i.e. if the
strength of magnetic field increases the force also increases
• strength of electric field (I) ~ directly proportional i.e. if the
strength of electric field increases the force also increases
• Length of conductor(L) ~ directly proportional i.e. if the length
of conductor increases the force also increases
𝐹 = 𝐵𝐼𝐿
• Activity 13.7 (page 230)ncert
A small aluminium rod is suspended horizontally from a stand using two connecting wires. Place
a strong horseshoe magnet in such a way that the rod lies between the two poles with the
magnetic field directed upwards. For this, put the north pole of the magnet vertically below and
south pole vertically above the aluminium rod. Connect the aluminium rod in series with a
battery, a key and a rheostat. Pass a current through the aluminium rod from one end to other
(B to A). The rod is displaced towards left. When the direction of current flowing through the rod
is reversed, the displacement of rod is towards right.
August 5, 2020deepsha 22

23. Activity 13.7
August 5, 2020deepsha 23

24. ELECTROMAGNETIC INDUCTION
• EMI is the phenomena due to which an
induced current is set up in a closed coil
whenever the magnetic field around it is
changing .
• Induced current lasts as long as the
change in magnetic field continues.
• As soon as, the magnetic field reaches
either a steady value or 0 the current
becomes 0.
• It is given by~ Flemings Right Hand
Rule.
MichaelFaraday
Moving magnet can be
used to generate electric
current
August 5, 2020deepsha 24

25. FLEMINGS RIGHT HAND RULE
• “Hold the right hand fore finger, middle finger and the thumb at right angles
to each other. If the forefinger represents the direction of the magnetic field,
the thumb points in the direction of motion or applied force, then the middle
finger points in the direction of the induced current.”
August 5, 2020deepsha 25
This Photo by Unknown Author is licensed under CC BY-SA
This Photo by Unknown Author is licensed under CC BY-SA

26. Fleming again
• Faraday did the impossible
• Had current with coil and not crucible
• He created magic for a moment
• Where changing magnetic field induced current
• U write Mother Board Inter
• From thumb to two finger
Now this rule is clear and right
Like fleming be wise and bright
August 5, 2020deepsha 26

27. MOTOR
• Definition- Motors convert electric energy to mechanical work.
• Structure- A power supply -A simple motor usually has a DC power source. It supplies power to the motor
armature or field coils.
Field Magnet could be a permanent magnet or an electromagnet
Armature or rotor Holds the armature coil in place ,provides mechanical support.
Commutator rotating interface of the armature coil with a stationary circuit.
Brushes conducts current between stationary wires and moving parts
Axle
• Working- Take two bar magnets and keep the poles facing each other with a small space in between.
Now, take a small length of a conducting wire and make a loop. Keep this loop in between the space
between the magnets such that it is still within the sphere of influence of the magnets. Now for the last bit.
Connect the ends of the loop to battery terminals.
• Uses- Drills
Water Pumps
August 5, 2020deepsha 27

28. Working: Let the current in the coil ABCD of
motor enters from the source battery
through the conducting brush X, flow along
ABCD and finally flows back to the battery
through brush Y. On applying Fleming’s left-
hand rule we find that force acting on arm
AB due to magnetic field pushes it
downwards. But the force acting on arm CD
pushes it upwards. Thus, the coil and the
axle rotate anticlockwise. Due to action of
split rings P and Q change their contacts
with brushes. Now, P makes contact with Y
and Q with X. As a result, Current begins to
flow in coil along DCBA. The arms are
pushed in opposite direction and coil
continues to rotate in same direction. August 5, 2020deepsha 28

29. Motor
August 5, 2020deepsha 29