Magnetic effect of current - 1 PPT Physics Class 12

 Page 1


MAGNETIC EFFECT OF CURRENT - I
1. Magnetic Effect of Current – Oersted’s Experiment
2. Ampere’s Swimming Rule
3. Maxwell’s Cork Screw Rule
4. Right Hand Thumb Rule
5. Biot – Savart’s Law
6. Magnetic Field due to Infinitely Long Straight Current –
carrying Conductor
7. Magnetic Field due to a Circular Loop carrying current
8. Magnetic Field due to a Solenoid
Page 2


MAGNETIC EFFECT OF CURRENT - I
1. Magnetic Effect of Current – Oersted’s Experiment
2. Ampere’s Swimming Rule
3. Maxwell’s Cork Screw Rule
4. Right Hand Thumb Rule
5. Biot – Savart’s Law
6. Magnetic Field due to Infinitely Long Straight Current –
carrying Conductor
7. Magnetic Field due to a Circular Loop carrying current
8. Magnetic Field due to a Solenoid
N
Magnetic Effect of Current:
An electric current (i.e. flow of electric charge) produces magnetic  effect in 
the space around the conductor called strength of Magnetic field or simply 
Magnetic field.
Oersted’s Experiment:
When current was allowed to flow through a 
wire  placed parallel to the axis of a magnetic 
needle kept directly below the wire, the needle 
was found to deflect from its normal position.
E
K
I
N
E
When current was reversed through the wire, 
the needle was found to deflect in the 
opposite direction to the earlier case.
K
I
Page 3


MAGNETIC EFFECT OF CURRENT - I
1. Magnetic Effect of Current – Oersted’s Experiment
2. Ampere’s Swimming Rule
3. Maxwell’s Cork Screw Rule
4. Right Hand Thumb Rule
5. Biot – Savart’s Law
6. Magnetic Field due to Infinitely Long Straight Current –
carrying Conductor
7. Magnetic Field due to a Circular Loop carrying current
8. Magnetic Field due to a Solenoid
N
Magnetic Effect of Current:
An electric current (i.e. flow of electric charge) produces magnetic  effect in 
the space around the conductor called strength of Magnetic field or simply 
Magnetic field.
Oersted’s Experiment:
When current was allowed to flow through a 
wire  placed parallel to the axis of a magnetic 
needle kept directly below the wire, the needle 
was found to deflect from its normal position.
E
K
I
N
E
When current was reversed through the wire, 
the needle was found to deflect in the 
opposite direction to the earlier case.
K
I
B B
Rules to determine the direction of magnetic field:    
Ampere’s Swimming Rule or
SNOW Rule:
Imagining a man who swims in the 
direction of current from south to north 
facing a magnetic needle kept under 
him such that current enters his feet 
then the North pole of the needle will 
deflect towards his left hand, i.e. 
towards West.
Maxwell’s Cork Screw Rule or Right 
Hand Screw Rule:
If the forward motion of an imaginary 
right handed screw is in the direction of 
the current through a linear conductor, 
then the direction of rotation of the 
screw gives the direction of the 
magnetic lines of force around the 
conductor.
S
I
I I
Page 4


MAGNETIC EFFECT OF CURRENT - I
1. Magnetic Effect of Current – Oersted’s Experiment
2. Ampere’s Swimming Rule
3. Maxwell’s Cork Screw Rule
4. Right Hand Thumb Rule
5. Biot – Savart’s Law
6. Magnetic Field due to Infinitely Long Straight Current –
carrying Conductor
7. Magnetic Field due to a Circular Loop carrying current
8. Magnetic Field due to a Solenoid
N
Magnetic Effect of Current:
An electric current (i.e. flow of electric charge) produces magnetic  effect in 
the space around the conductor called strength of Magnetic field or simply 
Magnetic field.
Oersted’s Experiment:
When current was allowed to flow through a 
wire  placed parallel to the axis of a magnetic 
needle kept directly below the wire, the needle 
was found to deflect from its normal position.
E
K
I
N
E
When current was reversed through the wire, 
the needle was found to deflect in the 
opposite direction to the earlier case.
K
I
B B
Rules to determine the direction of magnetic field:    
Ampere’s Swimming Rule or
SNOW Rule:
Imagining a man who swims in the 
direction of current from south to north 
facing a magnetic needle kept under 
him such that current enters his feet 
then the North pole of the needle will 
deflect towards his left hand, i.e. 
towards West.
Maxwell’s Cork Screw Rule or Right 
Hand Screw Rule:
If the forward motion of an imaginary 
right handed screw is in the direction of 
the current through a linear conductor, 
then the direction of rotation of the 
screw gives the direction of the 
magnetic lines of force around the 
conductor.
S
I
I I
x
Right Hand Thumb Rule or Curl Rule:
If a current carrying conductor is imagined to be 
held in the right hand such that the thumb points 
in the direction of the current, then the tips of the 
fingers encircling the conductor will give the 
direction of the magnetic lines of force.
I
Biot – Savart’s Law:
The strength of magnetic field  dB due to a small 
current element dl carrying a current I at a point 
P distant r from the element is directly 
proportional to I, dl, sin ? and inversely 
proportional to the square of the distance (r
2
) 
where ? is the angle between dl and r. 
?
P
dl
r
i)   dB a I
ii)  dB a dl
iii) dB a sin ?
iv) dB a 1 / r
2
dB a
I dl sin ?
r
2
dB =
µ
0   
I dl sin ?
4p r
2
P’
B
I
Page 5


MAGNETIC EFFECT OF CURRENT - I
1. Magnetic Effect of Current – Oersted’s Experiment
2. Ampere’s Swimming Rule
3. Maxwell’s Cork Screw Rule
4. Right Hand Thumb Rule
5. Biot – Savart’s Law
6. Magnetic Field due to Infinitely Long Straight Current –
carrying Conductor
7. Magnetic Field due to a Circular Loop carrying current
8. Magnetic Field due to a Solenoid
N
Magnetic Effect of Current:
An electric current (i.e. flow of electric charge) produces magnetic  effect in 
the space around the conductor called strength of Magnetic field or simply 
Magnetic field.
Oersted’s Experiment:
When current was allowed to flow through a 
wire  placed parallel to the axis of a magnetic 
needle kept directly below the wire, the needle 
was found to deflect from its normal position.
E
K
I
N
E
When current was reversed through the wire, 
the needle was found to deflect in the 
opposite direction to the earlier case.
K
I
B B
Rules to determine the direction of magnetic field:    
Ampere’s Swimming Rule or
SNOW Rule:
Imagining a man who swims in the 
direction of current from south to north 
facing a magnetic needle kept under 
him such that current enters his feet 
then the North pole of the needle will 
deflect towards his left hand, i.e. 
towards West.
Maxwell’s Cork Screw Rule or Right 
Hand Screw Rule:
If the forward motion of an imaginary 
right handed screw is in the direction of 
the current through a linear conductor, 
then the direction of rotation of the 
screw gives the direction of the 
magnetic lines of force around the 
conductor.
S
I
I I
x
Right Hand Thumb Rule or Curl Rule:
If a current carrying conductor is imagined to be 
held in the right hand such that the thumb points 
in the direction of the current, then the tips of the 
fingers encircling the conductor will give the 
direction of the magnetic lines of force.
I
Biot – Savart’s Law:
The strength of magnetic field  dB due to a small 
current element dl carrying a current I at a point 
P distant r from the element is directly 
proportional to I, dl, sin ? and inversely 
proportional to the square of the distance (r
2
) 
where ? is the angle between dl and r. 
?
P
dl
r
i)   dB a I
ii)  dB a dl
iii) dB a sin ?
iv) dB a 1 / r
2
dB a
I dl sin ?
r
2
dB =
µ
0   
I dl sin ?
4p r
2
P’
B
I
Biot – Savart’s Law in vector form:
dB =
µ
0   
I dl x r
4p r
2
dB =
µ
0   
I dl x r
4p r
3
Value of µ
0
= 4p x 10
-7
Tm A
-1
or Wb m
-1
A
-1
Direction of dB is same as that of direction of dl x r which can be 
determined by Right Hand Screw Rule.
It is emerging       at P’ and entering       at P into the plane of the diagram.
Current element is a vector quantity whose magnitude is the vector 
product of current and length of small element having the direction of the 
flow of current. ( I dl)
x