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3790-3793
20) B = m0n I = 4p × 10–7 × 103 × 5 = 6 28 × 10–3 T FIGURE 4 17 Two long straight parallel conductors carrying steady currents Ia and Ib and separated by a distance d Ba is the magnetic field set up by conductor ‘a’ at conductor ‘b’
1
3791-3794
28 × 10–3 T FIGURE 4 17 Two long straight parallel conductors carrying steady currents Ia and Ib and separated by a distance d Ba is the magnetic field set up by conductor ‘a’ at conductor ‘b’ 4
1
3792-3795
17 Two long straight parallel conductors carrying steady currents Ia and Ib and separated by a distance d Ba is the magnetic field set up by conductor ‘a’ at conductor ‘b’ 4 8 FORCE BETWEEN TWO PARALLEL CURRENTS, THE AMPERE We have learnt that there exists a magnetic field due to a conductor carrying a current which obeys the Biot-Savart law
1
3793-3796
Ba is the magnetic field set up by conductor ‘a’ at conductor ‘b’ 4 8 FORCE BETWEEN TWO PARALLEL CURRENTS, THE AMPERE We have learnt that there exists a magnetic field due to a conductor carrying a current which obeys the Biot-Savart law Further, we have learnt that an external magnetic field will exert a force on a current-carrying conductor
1
3794-3797
4 8 FORCE BETWEEN TWO PARALLEL CURRENTS, THE AMPERE We have learnt that there exists a magnetic field due to a conductor carrying a current which obeys the Biot-Savart law Further, we have learnt that an external magnetic field will exert a force on a current-carrying conductor This follows from the Lorentz force formula
1
3795-3798
8 FORCE BETWEEN TWO PARALLEL CURRENTS, THE AMPERE We have learnt that there exists a magnetic field due to a conductor carrying a current which obeys the Biot-Savart law Further, we have learnt that an external magnetic field will exert a force on a current-carrying conductor This follows from the Lorentz force formula Thus, it is logical to expect that two current-carrying conductors placed near each other will exert (magnetic) forces on each other
1
3796-3799
Further, we have learnt that an external magnetic field will exert a force on a current-carrying conductor This follows from the Lorentz force formula Thus, it is logical to expect that two current-carrying conductors placed near each other will exert (magnetic) forces on each other In the period 1820-25, Ampere studied the nature of this magnetic force and its dependence on the magnitude of the current, on the shape and size of the conductors, as well as, the distances between the conductors
1
3797-3800
This follows from the Lorentz force formula Thus, it is logical to expect that two current-carrying conductors placed near each other will exert (magnetic) forces on each other In the period 1820-25, Ampere studied the nature of this magnetic force and its dependence on the magnitude of the current, on the shape and size of the conductors, as well as, the distances between the conductors In this section, we shall take the simple example of two parallel current- carrying conductors, which will perhaps help us to appreciate Ampere’s painstaking work
1
3798-3801
Thus, it is logical to expect that two current-carrying conductors placed near each other will exert (magnetic) forces on each other In the period 1820-25, Ampere studied the nature of this magnetic force and its dependence on the magnitude of the current, on the shape and size of the conductors, as well as, the distances between the conductors In this section, we shall take the simple example of two parallel current- carrying conductors, which will perhaps help us to appreciate Ampere’s painstaking work Rationalised 2023-24 123 Moving Charges and Magnetism Figure 4
1
3799-3802
In the period 1820-25, Ampere studied the nature of this magnetic force and its dependence on the magnitude of the current, on the shape and size of the conductors, as well as, the distances between the conductors In this section, we shall take the simple example of two parallel current- carrying conductors, which will perhaps help us to appreciate Ampere’s painstaking work Rationalised 2023-24 123 Moving Charges and Magnetism Figure 4 17 shows two long parallel conductors a and b separated by a distance d and carrying (parallel) currents Ia and Ib, respectively
1
3800-3803
In this section, we shall take the simple example of two parallel current- carrying conductors, which will perhaps help us to appreciate Ampere’s painstaking work Rationalised 2023-24 123 Moving Charges and Magnetism Figure 4 17 shows two long parallel conductors a and b separated by a distance d and carrying (parallel) currents Ia and Ib, respectively The conductor ‘a’ produces, the same magnetic field Ba at all points along the conductor ‘b’
1
3801-3804
Rationalised 2023-24 123 Moving Charges and Magnetism Figure 4 17 shows two long parallel conductors a and b separated by a distance d and carrying (parallel) currents Ia and Ib, respectively The conductor ‘a’ produces, the same magnetic field Ba at all points along the conductor ‘b’ The right-hand rule tells us that the direction of this field is downwards (when the conductors are placed horizontally)
1
3802-3805
17 shows two long parallel conductors a and b separated by a distance d and carrying (parallel) currents Ia and Ib, respectively The conductor ‘a’ produces, the same magnetic field Ba at all points along the conductor ‘b’ The right-hand rule tells us that the direction of this field is downwards (when the conductors are placed horizontally) Its magnitude is given by Eq
1
3803-3806
The conductor ‘a’ produces, the same magnetic field Ba at all points along the conductor ‘b’ The right-hand rule tells us that the direction of this field is downwards (when the conductors are placed horizontally) Its magnitude is given by Eq [4
1
3804-3807
The right-hand rule tells us that the direction of this field is downwards (when the conductors are placed horizontally) Its magnitude is given by Eq [4 19(a)] or from Ampere’s circuital law, 0 2 a a I B d =µ π The conductor ‘b’ carrying a current Ib will experience a sideways force due to the field Ba
1
3805-3808
Its magnitude is given by Eq [4 19(a)] or from Ampere’s circuital law, 0 2 a a I B d =µ π The conductor ‘b’ carrying a current Ib will experience a sideways force due to the field Ba The direction of this force is towards the conductor ‘a’ (Verify this)
1
3806-3809
[4 19(a)] or from Ampere’s circuital law, 0 2 a a I B d =µ π The conductor ‘b’ carrying a current Ib will experience a sideways force due to the field Ba The direction of this force is towards the conductor ‘a’ (Verify this) We label this force as Fba, the force on a segment L of ‘b’ due to ‘a’
1
3807-3810
19(a)] or from Ampere’s circuital law, 0 2 a a I B d =µ π The conductor ‘b’ carrying a current Ib will experience a sideways force due to the field Ba The direction of this force is towards the conductor ‘a’ (Verify this) We label this force as Fba, the force on a segment L of ‘b’ due to ‘a’ The magnitude of this force is given by Eq
1
3808-3811
The direction of this force is towards the conductor ‘a’ (Verify this) We label this force as Fba, the force on a segment L of ‘b’ due to ‘a’ The magnitude of this force is given by Eq (4
1
3809-3812
We label this force as Fba, the force on a segment L of ‘b’ due to ‘a’ The magnitude of this force is given by Eq (4 4), Fba = Ib L Ba 0 2 a I Ib L d =µ π (4
1
3810-3813
The magnitude of this force is given by Eq (4 4), Fba = Ib L Ba 0 2 a I Ib L d =µ π (4 23) It is of course possible to compute the force on ‘a’ due to ‘b’
1
3811-3814
(4 4), Fba = Ib L Ba 0 2 a I Ib L d =µ π (4 23) It is of course possible to compute the force on ‘a’ due to ‘b’ From considerations similar to above we can find the force Fab, on a segment of length L of ‘a’ due to the current in ‘b’
1
3812-3815
4), Fba = Ib L Ba 0 2 a I Ib L d =µ π (4 23) It is of course possible to compute the force on ‘a’ due to ‘b’ From considerations similar to above we can find the force Fab, on a segment of length L of ‘a’ due to the current in ‘b’ It is equal in magnitude to Fba, and directed towards ‘b’
1
3813-3816
23) It is of course possible to compute the force on ‘a’ due to ‘b’ From considerations similar to above we can find the force Fab, on a segment of length L of ‘a’ due to the current in ‘b’ It is equal in magnitude to Fba, and directed towards ‘b’ Thus, Fba = –Fab (4
1
3814-3817
From considerations similar to above we can find the force Fab, on a segment of length L of ‘a’ due to the current in ‘b’ It is equal in magnitude to Fba, and directed towards ‘b’ Thus, Fba = –Fab (4 24) Note that this is consistent with Newton’s third Law
1
3815-3818
It is equal in magnitude to Fba, and directed towards ‘b’ Thus, Fba = –Fab (4 24) Note that this is consistent with Newton’s third Law Thus, at least for parallel conductors and steady currents, we have shown that the Biot-Savart law and the Lorentz force yield results in accordance with Newton’s third Law*
1
3816-3819
Thus, Fba = –Fab (4 24) Note that this is consistent with Newton’s third Law Thus, at least for parallel conductors and steady currents, we have shown that the Biot-Savart law and the Lorentz force yield results in accordance with Newton’s third Law* We have seen from above that currents flowing in the same direction attract each other
1
3817-3820
24) Note that this is consistent with Newton’s third Law Thus, at least for parallel conductors and steady currents, we have shown that the Biot-Savart law and the Lorentz force yield results in accordance with Newton’s third Law* We have seen from above that currents flowing in the same direction attract each other One can show that oppositely directed currents repel each other
1
3818-3821
Thus, at least for parallel conductors and steady currents, we have shown that the Biot-Savart law and the Lorentz force yield results in accordance with Newton’s third Law* We have seen from above that currents flowing in the same direction attract each other One can show that oppositely directed currents repel each other Thus, Parallel currents attract, and antiparallel currents repel
1
3819-3822
We have seen from above that currents flowing in the same direction attract each other One can show that oppositely directed currents repel each other Thus, Parallel currents attract, and antiparallel currents repel This rule is the opposite of what we find in electrostatics
1
3820-3823
One can show that oppositely directed currents repel each other Thus, Parallel currents attract, and antiparallel currents repel This rule is the opposite of what we find in electrostatics Like (same sign) charges repel each other, but like (parallel) currents attract each other
1
3821-3824
Thus, Parallel currents attract, and antiparallel currents repel This rule is the opposite of what we find in electrostatics Like (same sign) charges repel each other, but like (parallel) currents attract each other Let fba represent the magnitude of the force Fba per unit length
1
3822-3825
This rule is the opposite of what we find in electrostatics Like (same sign) charges repel each other, but like (parallel) currents attract each other Let fba represent the magnitude of the force Fba per unit length Then, from Eq
1
3823-3826
Like (same sign) charges repel each other, but like (parallel) currents attract each other Let fba represent the magnitude of the force Fba per unit length Then, from Eq (4
1
3824-3827
Let fba represent the magnitude of the force Fba per unit length Then, from Eq (4 23), π 0 2 a b ba I I f d =µ (4
1
3825-3828
Then, from Eq (4 23), π 0 2 a b ba I I f d =µ (4 25) The above expression is used to define the ampere (A), which is one of the seven SI base units
1
3826-3829
(4 23), π 0 2 a b ba I I f d =µ (4 25) The above expression is used to define the ampere (A), which is one of the seven SI base units * It turns out that when we have time-dependent currents and/or charges in motion, Newton’s third law may not hold for forces between charges and/or conductors
1
3827-3830
23), π 0 2 a b ba I I f d =µ (4 25) The above expression is used to define the ampere (A), which is one of the seven SI base units * It turns out that when we have time-dependent currents and/or charges in motion, Newton’s third law may not hold for forces between charges and/or conductors An essential consequence of the Newton’s third law in mechanics is conservation of momentum of an isolated system
1
3828-3831
25) The above expression is used to define the ampere (A), which is one of the seven SI base units * It turns out that when we have time-dependent currents and/or charges in motion, Newton’s third law may not hold for forces between charges and/or conductors An essential consequence of the Newton’s third law in mechanics is conservation of momentum of an isolated system This, however, holds even for the case of time-dependent situations with electromagnetic fields, provided the momentum carried by fields is also taken into account
1
3829-3832
* It turns out that when we have time-dependent currents and/or charges in motion, Newton’s third law may not hold for forces between charges and/or conductors An essential consequence of the Newton’s third law in mechanics is conservation of momentum of an isolated system This, however, holds even for the case of time-dependent situations with electromagnetic fields, provided the momentum carried by fields is also taken into account Rationalised 2023-24 Physics 124 EXAMPLE 4
1
3830-3833
An essential consequence of the Newton’s third law in mechanics is conservation of momentum of an isolated system This, however, holds even for the case of time-dependent situations with electromagnetic fields, provided the momentum carried by fields is also taken into account Rationalised 2023-24 Physics 124 EXAMPLE 4 10 The ampere is the value of that steady current which, when maintained in each of the two very long, straight, parallel conductors of negligible cross-section, and placed one metre apart in vacuum, would produce on each of these conductors a force equal to 2 × 10–7 newtons per metre of length
1
3831-3834
This, however, holds even for the case of time-dependent situations with electromagnetic fields, provided the momentum carried by fields is also taken into account Rationalised 2023-24 Physics 124 EXAMPLE 4 10 The ampere is the value of that steady current which, when maintained in each of the two very long, straight, parallel conductors of negligible cross-section, and placed one metre apart in vacuum, would produce on each of these conductors a force equal to 2 × 10–7 newtons per metre of length This definition of the ampere was adopted in 1946
1
3832-3835
Rationalised 2023-24 Physics 124 EXAMPLE 4 10 The ampere is the value of that steady current which, when maintained in each of the two very long, straight, parallel conductors of negligible cross-section, and placed one metre apart in vacuum, would produce on each of these conductors a force equal to 2 × 10–7 newtons per metre of length This definition of the ampere was adopted in 1946 It is a theoretical definition
1
3833-3836
10 The ampere is the value of that steady current which, when maintained in each of the two very long, straight, parallel conductors of negligible cross-section, and placed one metre apart in vacuum, would produce on each of these conductors a force equal to 2 × 10–7 newtons per metre of length This definition of the ampere was adopted in 1946 It is a theoretical definition In practice, one must eliminate the effect of the earth’s magnetic field and substitute very long wires by multiturn coils of appropriate geometries
1
3834-3837
This definition of the ampere was adopted in 1946 It is a theoretical definition In practice, one must eliminate the effect of the earth’s magnetic field and substitute very long wires by multiturn coils of appropriate geometries An instrument called the current balance is used to measure this mechanical force
1
3835-3838
It is a theoretical definition In practice, one must eliminate the effect of the earth’s magnetic field and substitute very long wires by multiturn coils of appropriate geometries An instrument called the current balance is used to measure this mechanical force The SI unit of charge, namely, the coulomb, can now be defined in terms of the ampere
1
3836-3839
In practice, one must eliminate the effect of the earth’s magnetic field and substitute very long wires by multiturn coils of appropriate geometries An instrument called the current balance is used to measure this mechanical force The SI unit of charge, namely, the coulomb, can now be defined in terms of the ampere When a steady current of 1A is set up in a conductor, the quantity of charge that flows through its cross-section in 1s is one coulomb (1C)
1
3837-3840
An instrument called the current balance is used to measure this mechanical force The SI unit of charge, namely, the coulomb, can now be defined in terms of the ampere When a steady current of 1A is set up in a conductor, the quantity of charge that flows through its cross-section in 1s is one coulomb (1C) Example 4
1
3838-3841
The SI unit of charge, namely, the coulomb, can now be defined in terms of the ampere When a steady current of 1A is set up in a conductor, the quantity of charge that flows through its cross-section in 1s is one coulomb (1C) Example 4 10 The horizontal component of the earth’s magnetic field at a certain place is 3
1
3839-3842
When a steady current of 1A is set up in a conductor, the quantity of charge that flows through its cross-section in 1s is one coulomb (1C) Example 4 10 The horizontal component of the earth’s magnetic field at a certain place is 3 0 ×10–5 T and the direction of the field is from the geographic south to the geographic north
1
3840-3843
Example 4 10 The horizontal component of the earth’s magnetic field at a certain place is 3 0 ×10–5 T and the direction of the field is from the geographic south to the geographic north A very long straight conductor is carrying a steady current of 1A
1
3841-3844
10 The horizontal component of the earth’s magnetic field at a certain place is 3 0 ×10–5 T and the direction of the field is from the geographic south to the geographic north A very long straight conductor is carrying a steady current of 1A What is the force per unit length on it when it is placed on a horizontal table and the direction of the current is (a) east to west; (b) south to north
1
3842-3845
0 ×10–5 T and the direction of the field is from the geographic south to the geographic north A very long straight conductor is carrying a steady current of 1A What is the force per unit length on it when it is placed on a horizontal table and the direction of the current is (a) east to west; (b) south to north Solution F = Il × B F = IlB sinq The force per unit length is f = F/l = I B sinq (a) When the current is flowing from east to west, q = 90° Hence, f = I B = 1 × 3 × 10–5 = 3 × 10–5 N m–1 This is larger than the value 2×10–7 Nm–1 quoted in the definition of the ampere
1
3843-3846
A very long straight conductor is carrying a steady current of 1A What is the force per unit length on it when it is placed on a horizontal table and the direction of the current is (a) east to west; (b) south to north Solution F = Il × B F = IlB sinq The force per unit length is f = F/l = I B sinq (a) When the current is flowing from east to west, q = 90° Hence, f = I B = 1 × 3 × 10–5 = 3 × 10–5 N m–1 This is larger than the value 2×10–7 Nm–1 quoted in the definition of the ampere Hence it is important to eliminate the effect of the earth’s magnetic field and other stray fields while standardising the ampere
1
3844-3847
What is the force per unit length on it when it is placed on a horizontal table and the direction of the current is (a) east to west; (b) south to north Solution F = Il × B F = IlB sinq The force per unit length is f = F/l = I B sinq (a) When the current is flowing from east to west, q = 90° Hence, f = I B = 1 × 3 × 10–5 = 3 × 10–5 N m–1 This is larger than the value 2×10–7 Nm–1 quoted in the definition of the ampere Hence it is important to eliminate the effect of the earth’s magnetic field and other stray fields while standardising the ampere The direction of the force is downwards
1
3845-3848
Solution F = Il × B F = IlB sinq The force per unit length is f = F/l = I B sinq (a) When the current is flowing from east to west, q = 90° Hence, f = I B = 1 × 3 × 10–5 = 3 × 10–5 N m–1 This is larger than the value 2×10–7 Nm–1 quoted in the definition of the ampere Hence it is important to eliminate the effect of the earth’s magnetic field and other stray fields while standardising the ampere The direction of the force is downwards This direction may be obtained by the directional property of cross product of vectors
1
3846-3849
Hence it is important to eliminate the effect of the earth’s magnetic field and other stray fields while standardising the ampere The direction of the force is downwards This direction may be obtained by the directional property of cross product of vectors (b) When the current is flowing from south to north, q = 0o f = 0 Hence there is no force on the conductor
1
3847-3850
The direction of the force is downwards This direction may be obtained by the directional property of cross product of vectors (b) When the current is flowing from south to north, q = 0o f = 0 Hence there is no force on the conductor 4
1
3848-3851
This direction may be obtained by the directional property of cross product of vectors (b) When the current is flowing from south to north, q = 0o f = 0 Hence there is no force on the conductor 4 9 TORQUE ON CURRENT LOOP, MAGNETIC DIPOLE 4
1
3849-3852
(b) When the current is flowing from south to north, q = 0o f = 0 Hence there is no force on the conductor 4 9 TORQUE ON CURRENT LOOP, MAGNETIC DIPOLE 4 9
1
3850-3853
4 9 TORQUE ON CURRENT LOOP, MAGNETIC DIPOLE 4 9 1 Torque on a rectangular current loop in a uniform magnetic field We now show that a rectangular loop carrying a steady current I and placed in a uniform magnetic field experiences a torque
1
3851-3854
9 TORQUE ON CURRENT LOOP, MAGNETIC DIPOLE 4 9 1 Torque on a rectangular current loop in a uniform magnetic field We now show that a rectangular loop carrying a steady current I and placed in a uniform magnetic field experiences a torque It does not experience a net force
1
3852-3855
9 1 Torque on a rectangular current loop in a uniform magnetic field We now show that a rectangular loop carrying a steady current I and placed in a uniform magnetic field experiences a torque It does not experience a net force This behaviour is analogous to that of electric dipole in a uniform electric field (Section 1
1
3853-3856
1 Torque on a rectangular current loop in a uniform magnetic field We now show that a rectangular loop carrying a steady current I and placed in a uniform magnetic field experiences a torque It does not experience a net force This behaviour is analogous to that of electric dipole in a uniform electric field (Section 1 12)
1
3854-3857
It does not experience a net force This behaviour is analogous to that of electric dipole in a uniform electric field (Section 1 12) Rationalised 2023-24 125 Moving Charges and Magnetism We first consider the simple case when the rectangular loop is placed such that the uniform magnetic field B is in the plane of the loop
1
3855-3858
This behaviour is analogous to that of electric dipole in a uniform electric field (Section 1 12) Rationalised 2023-24 125 Moving Charges and Magnetism We first consider the simple case when the rectangular loop is placed such that the uniform magnetic field B is in the plane of the loop This is illustrated in Fig
1
3856-3859
12) Rationalised 2023-24 125 Moving Charges and Magnetism We first consider the simple case when the rectangular loop is placed such that the uniform magnetic field B is in the plane of the loop This is illustrated in Fig 4
1
3857-3860
Rationalised 2023-24 125 Moving Charges and Magnetism We first consider the simple case when the rectangular loop is placed such that the uniform magnetic field B is in the plane of the loop This is illustrated in Fig 4 18(a)
1
3858-3861
This is illustrated in Fig 4 18(a) The field exerts no force on the two arms AD and BC of the loop
1
3859-3862
4 18(a) The field exerts no force on the two arms AD and BC of the loop It is perpendicular to the arm AB of the loop and exerts a force F1 on it which is directed into the plane of the loop
1
3860-3863
18(a) The field exerts no force on the two arms AD and BC of the loop It is perpendicular to the arm AB of the loop and exerts a force F1 on it which is directed into the plane of the loop Its magnitude is, F1 = I b B Similarly, it exerts a force F2 on the arm CD and F2 is directed out of the plane of the paper
1
3861-3864
The field exerts no force on the two arms AD and BC of the loop It is perpendicular to the arm AB of the loop and exerts a force F1 on it which is directed into the plane of the loop Its magnitude is, F1 = I b B Similarly, it exerts a force F2 on the arm CD and F2 is directed out of the plane of the paper F2 = I b B = F1 Thus, the net force on the loop is zero
1
3862-3865
It is perpendicular to the arm AB of the loop and exerts a force F1 on it which is directed into the plane of the loop Its magnitude is, F1 = I b B Similarly, it exerts a force F2 on the arm CD and F2 is directed out of the plane of the paper F2 = I b B = F1 Thus, the net force on the loop is zero There is a torque on the loop due to the pair of forces F1 and F2
1
3863-3866
Its magnitude is, F1 = I b B Similarly, it exerts a force F2 on the arm CD and F2 is directed out of the plane of the paper F2 = I b B = F1 Thus, the net force on the loop is zero There is a torque on the loop due to the pair of forces F1 and F2 Figure 4
1
3864-3867
F2 = I b B = F1 Thus, the net force on the loop is zero There is a torque on the loop due to the pair of forces F1 and F2 Figure 4 18(b) shows a view of the loop from the AD end
1
3865-3868
There is a torque on the loop due to the pair of forces F1 and F2 Figure 4 18(b) shows a view of the loop from the AD end It shows that the torque on the loop tends to rotate it anticlockwise
1
3866-3869
Figure 4 18(b) shows a view of the loop from the AD end It shows that the torque on the loop tends to rotate it anticlockwise This torque is (in magnitude), 1 2 2 2 a a F F τ = + ( ) 2 2 a a IbB IbB I ab B = + = = I A B (4
1
3867-3870
18(b) shows a view of the loop from the AD end It shows that the torque on the loop tends to rotate it anticlockwise This torque is (in magnitude), 1 2 2 2 a a F F τ = + ( ) 2 2 a a IbB IbB I ab B = + = = I A B (4 26) where A = ab is the area of the rectangle
1
3868-3871
It shows that the torque on the loop tends to rotate it anticlockwise This torque is (in magnitude), 1 2 2 2 a a F F τ = + ( ) 2 2 a a IbB IbB I ab B = + = = I A B (4 26) where A = ab is the area of the rectangle We next consider the case when the plane of the loop, is not along the magnetic field, but makes an angle with it
1
3869-3872
This torque is (in magnitude), 1 2 2 2 a a F F τ = + ( ) 2 2 a a IbB IbB I ab B = + = = I A B (4 26) where A = ab is the area of the rectangle We next consider the case when the plane of the loop, is not along the magnetic field, but makes an angle with it We take the angle between the field and the normal to the coil to be angle q (The previous case corresponds to q = p/2)
1
3870-3873
26) where A = ab is the area of the rectangle We next consider the case when the plane of the loop, is not along the magnetic field, but makes an angle with it We take the angle between the field and the normal to the coil to be angle q (The previous case corresponds to q = p/2) Figure 4
1
3871-3874
We next consider the case when the plane of the loop, is not along the magnetic field, but makes an angle with it We take the angle between the field and the normal to the coil to be angle q (The previous case corresponds to q = p/2) Figure 4 19 illustrates this general case
1
3872-3875
We take the angle between the field and the normal to the coil to be angle q (The previous case corresponds to q = p/2) Figure 4 19 illustrates this general case The forces on the arms BC and DA are equal, opposite, and act along the axis of the coil, which connects the centres of mass of BC and DA
1
3873-3876
Figure 4 19 illustrates this general case The forces on the arms BC and DA are equal, opposite, and act along the axis of the coil, which connects the centres of mass of BC and DA Being collinear along the axis they cancel each other, resulting in no net force or torque
1
3874-3877
19 illustrates this general case The forces on the arms BC and DA are equal, opposite, and act along the axis of the coil, which connects the centres of mass of BC and DA Being collinear along the axis they cancel each other, resulting in no net force or torque The forces on arms AB and CD are F1 and F2
1
3875-3878
The forces on the arms BC and DA are equal, opposite, and act along the axis of the coil, which connects the centres of mass of BC and DA Being collinear along the axis they cancel each other, resulting in no net force or torque The forces on arms AB and CD are F1 and F2 They too are equal and opposite, with magnitude, F1 = F2 = I b B But they are not collinear
1
3876-3879
Being collinear along the axis they cancel each other, resulting in no net force or torque The forces on arms AB and CD are F1 and F2 They too are equal and opposite, with magnitude, F1 = F2 = I b B But they are not collinear This results in a couple as before
1
3877-3880
The forces on arms AB and CD are F1 and F2 They too are equal and opposite, with magnitude, F1 = F2 = I b B But they are not collinear This results in a couple as before The torque is, however, less than the earlier case when plane of loop was along the magnetic field
1
3878-3881
They too are equal and opposite, with magnitude, F1 = F2 = I b B But they are not collinear This results in a couple as before The torque is, however, less than the earlier case when plane of loop was along the magnetic field This is because the perpendicular distance between the forces of the couple has decreased
1
3879-3882
This results in a couple as before The torque is, however, less than the earlier case when plane of loop was along the magnetic field This is because the perpendicular distance between the forces of the couple has decreased Figure 4
1
3880-3883
The torque is, however, less than the earlier case when plane of loop was along the magnetic field This is because the perpendicular distance between the forces of the couple has decreased Figure 4 19(b) is a view of the arrangement from the AD end and it illustrates these two forces constituting a couple
1
3881-3884
This is because the perpendicular distance between the forces of the couple has decreased Figure 4 19(b) is a view of the arrangement from the AD end and it illustrates these two forces constituting a couple The magnitude of the torque on the loop is, 1 2 sin sin 2 2 a a F F τ θ θ = + = I ab B sin q = I A B sin q (4
1
3882-3885
Figure 4 19(b) is a view of the arrangement from the AD end and it illustrates these two forces constituting a couple The magnitude of the torque on the loop is, 1 2 sin sin 2 2 a a F F τ θ θ = + = I ab B sin q = I A B sin q (4 27) FIGURE 4
1
3883-3886
19(b) is a view of the arrangement from the AD end and it illustrates these two forces constituting a couple The magnitude of the torque on the loop is, 1 2 sin sin 2 2 a a F F τ θ θ = + = I ab B sin q = I A B sin q (4 27) FIGURE 4 18 (a) A rectangular current-carrying coil in uniform magnetic field
1
3884-3887
The magnitude of the torque on the loop is, 1 2 sin sin 2 2 a a F F τ θ θ = + = I ab B sin q = I A B sin q (4 27) FIGURE 4 18 (a) A rectangular current-carrying coil in uniform magnetic field The magnetic moment m points downwards
1
3885-3888
27) FIGURE 4 18 (a) A rectangular current-carrying coil in uniform magnetic field The magnetic moment m points downwards The torque ttttt is along the axis and tends to rotate the coil anticlockwise
1
3886-3889
18 (a) A rectangular current-carrying coil in uniform magnetic field The magnetic moment m points downwards The torque ttttt is along the axis and tends to rotate the coil anticlockwise (b) The couple acting on the coil
1
3887-3890
The magnetic moment m points downwards The torque ttttt is along the axis and tends to rotate the coil anticlockwise (b) The couple acting on the coil Rationalised 2023-24 Physics 126 EXAMPLE 4
1
3888-3891
The torque ttttt is along the axis and tends to rotate the coil anticlockwise (b) The couple acting on the coil Rationalised 2023-24 Physics 126 EXAMPLE 4 11 As q à 0, the perpendicular distance between the forces of the couple also approaches zero
1
3889-3892
(b) The couple acting on the coil Rationalised 2023-24 Physics 126 EXAMPLE 4 11 As q à 0, the perpendicular distance between the forces of the couple also approaches zero This makes the forces collinear and the net force and torque zero