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Page 1 MAGNETIC EFFECT OF CURRENT - II 1. Lorentz Magnetic Force 2. Fleming’s Left Hand Rule 3. Force on a moving charge in uniform Electric and Magnetic fields 4. Force on a current carrying conductor in a uniform Magnetic Field 5. Force between two infinitely long parallel current-carrying conductors 6. Definition of ampere 7. Representation of fields due to parallel currents 8. Torque experienced by a current-carrying coil in a uniform Magnetic Field 9. Moving Coil Galvanometer 10.Conversion of Galvanometer into Ammeter and Voltmeter 11.Differences between Ammeter and Voltmeter Page 2 MAGNETIC EFFECT OF CURRENT - II 1. Lorentz Magnetic Force 2. Fleming’s Left Hand Rule 3. Force on a moving charge in uniform Electric and Magnetic fields 4. Force on a current carrying conductor in a uniform Magnetic Field 5. Force between two infinitely long parallel current-carrying conductors 6. Definition of ampere 7. Representation of fields due to parallel currents 8. Torque experienced by a current-carrying coil in a uniform Magnetic Field 9. Moving Coil Galvanometer 10.Conversion of Galvanometer into Ammeter and Voltmeter 11.Differences between Ammeter and Voltmeter Lorentz Magnetic Force: A current carrying conductor placed in a magnetic field experiences a force which means that a moving charge in a magnetic field experiences force. F m = q (v x B) + q B v F I ? - q B v F ? F m = (q v B sin ?) n where ? is the angle between v and B Special Cases: i) If the charge is at rest, i.e. v = 0, then F m = 0. So, a stationary charge in a magnetic field does not experience any force. ii) If ? = 0° or 180° i.e. if the charge moves parallel or anti-parallel to the direction of the magnetic field, then F m = 0. iii) If ? = 90° i.e. if the charge moves perpendicular to the magnetic field, then the force is maximum. F m (max) = q v B or I Page 3 MAGNETIC EFFECT OF CURRENT - II 1. Lorentz Magnetic Force 2. Fleming’s Left Hand Rule 3. Force on a moving charge in uniform Electric and Magnetic fields 4. Force on a current carrying conductor in a uniform Magnetic Field 5. Force between two infinitely long parallel current-carrying conductors 6. Definition of ampere 7. Representation of fields due to parallel currents 8. Torque experienced by a current-carrying coil in a uniform Magnetic Field 9. Moving Coil Galvanometer 10.Conversion of Galvanometer into Ammeter and Voltmeter 11.Differences between Ammeter and Voltmeter Lorentz Magnetic Force: A current carrying conductor placed in a magnetic field experiences a force which means that a moving charge in a magnetic field experiences force. F m = q (v x B) + q B v F I ? - q B v F ? F m = (q v B sin ?) n where ? is the angle between v and B Special Cases: i) If the charge is at rest, i.e. v = 0, then F m = 0. So, a stationary charge in a magnetic field does not experience any force. ii) If ? = 0° or 180° i.e. if the charge moves parallel or anti-parallel to the direction of the magnetic field, then F m = 0. iii) If ? = 90° i.e. if the charge moves perpendicular to the magnetic field, then the force is maximum. F m (max) = q v B or I Fleming’s Left Hand Rule: Force (F) Magnetic Field (B) Electric Current (I) If the central finger, fore finger and thumb of left hand are stretched mutually perpendicular to each other and the central finger points to current, fore finger points to magnetic field, then thumb points in the direction of motion (force) on the current carrying conductor. TIP: Remember the phrase ‘e m f’ to represent electric current, magnetic field and force in anticlockwise direction of the fingers of left hand. Force on a moving charge in uniform Electric and Magnetic Fields: When a charge q moves with velocity v in region in which both electric field E and magnetic field B exist, then the Lorentz force is F = qE + q (v x B) or F = q (E + v x B) Page 4 MAGNETIC EFFECT OF CURRENT - II 1. Lorentz Magnetic Force 2. Fleming’s Left Hand Rule 3. Force on a moving charge in uniform Electric and Magnetic fields 4. Force on a current carrying conductor in a uniform Magnetic Field 5. Force between two infinitely long parallel current-carrying conductors 6. Definition of ampere 7. Representation of fields due to parallel currents 8. Torque experienced by a current-carrying coil in a uniform Magnetic Field 9. Moving Coil Galvanometer 10.Conversion of Galvanometer into Ammeter and Voltmeter 11.Differences between Ammeter and Voltmeter Lorentz Magnetic Force: A current carrying conductor placed in a magnetic field experiences a force which means that a moving charge in a magnetic field experiences force. F m = q (v x B) + q B v F I ? - q B v F ? F m = (q v B sin ?) n where ? is the angle between v and B Special Cases: i) If the charge is at rest, i.e. v = 0, then F m = 0. So, a stationary charge in a magnetic field does not experience any force. ii) If ? = 0° or 180° i.e. if the charge moves parallel or anti-parallel to the direction of the magnetic field, then F m = 0. iii) If ? = 90° i.e. if the charge moves perpendicular to the magnetic field, then the force is maximum. F m (max) = q v B or I Fleming’s Left Hand Rule: Force (F) Magnetic Field (B) Electric Current (I) If the central finger, fore finger and thumb of left hand are stretched mutually perpendicular to each other and the central finger points to current, fore finger points to magnetic field, then thumb points in the direction of motion (force) on the current carrying conductor. TIP: Remember the phrase ‘e m f’ to represent electric current, magnetic field and force in anticlockwise direction of the fingers of left hand. Force on a moving charge in uniform Electric and Magnetic Fields: When a charge q moves with velocity v in region in which both electric field E and magnetic field B exist, then the Lorentz force is F = qE + q (v x B) or F = q (E + v x B) Force on a current-carrying conductor in a uniform Magnetic Field: ? v d dl F I I B A l Force experienced by each electron in the conductor is f = - e (v d x B) If n be the number density of electrons, A be the area of cross section of the conductor, then no. of electrons in the element dl is n A dl. where I = neAv d and -ve sign represents that the direction of dl is opposite to that of v d ) or F = I l B sin ? - Force experienced by the electrons in dl is dF = n A dl [ - e (v d x B)] = - n e A v d (dl X B) = I (dl x B) F = ? dF = ? I (dl x B) F = I (l x B) Page 5 MAGNETIC EFFECT OF CURRENT - II 1. Lorentz Magnetic Force 2. Fleming’s Left Hand Rule 3. Force on a moving charge in uniform Electric and Magnetic fields 4. Force on a current carrying conductor in a uniform Magnetic Field 5. Force between two infinitely long parallel current-carrying conductors 6. Definition of ampere 7. Representation of fields due to parallel currents 8. Torque experienced by a current-carrying coil in a uniform Magnetic Field 9. Moving Coil Galvanometer 10.Conversion of Galvanometer into Ammeter and Voltmeter 11.Differences between Ammeter and Voltmeter Lorentz Magnetic Force: A current carrying conductor placed in a magnetic field experiences a force which means that a moving charge in a magnetic field experiences force. F m = q (v x B) + q B v F I ? - q B v F ? F m = (q v B sin ?) n where ? is the angle between v and B Special Cases: i) If the charge is at rest, i.e. v = 0, then F m = 0. So, a stationary charge in a magnetic field does not experience any force. ii) If ? = 0° or 180° i.e. if the charge moves parallel or anti-parallel to the direction of the magnetic field, then F m = 0. iii) If ? = 90° i.e. if the charge moves perpendicular to the magnetic field, then the force is maximum. F m (max) = q v B or I Fleming’s Left Hand Rule: Force (F) Magnetic Field (B) Electric Current (I) If the central finger, fore finger and thumb of left hand are stretched mutually perpendicular to each other and the central finger points to current, fore finger points to magnetic field, then thumb points in the direction of motion (force) on the current carrying conductor. TIP: Remember the phrase ‘e m f’ to represent electric current, magnetic field and force in anticlockwise direction of the fingers of left hand. Force on a moving charge in uniform Electric and Magnetic Fields: When a charge q moves with velocity v in region in which both electric field E and magnetic field B exist, then the Lorentz force is F = qE + q (v x B) or F = q (E + v x B) Force on a current-carrying conductor in a uniform Magnetic Field: ? v d dl F I I B A l Force experienced by each electron in the conductor is f = - e (v d x B) If n be the number density of electrons, A be the area of cross section of the conductor, then no. of electrons in the element dl is n A dl. where I = neAv d and -ve sign represents that the direction of dl is opposite to that of v d ) or F = I l B sin ? - Force experienced by the electrons in dl is dF = n A dl [ - e (v d x B)] = - n e A v d (dl X B) = I (dl x B) F = ? dF = ? I (dl x B) F = I (l x B) Forces between two parallel infinitely long current-carrying conductors: r F 21 F 12 I 1 P Q I 2 S R B 1 = µ 0 I 1 2p r Magnetic Field on RS due to current in PQ is Force acting on RS due to current I 2 through it is F 21 = µ 0 I 1 2p r I 2 l sin 90° B 1 acts perpendicular and into the plane of the diagram by Right Hand Thumb Rule. So, the angle between l and B 1 is 90° . l is length of the conductor. F 21 = µ 0 I 1 I 2 l 2p r B 2 = µ 0 I 2 2p r Magnetic Field on PQ due to current in RS is Force acting on PQ due to current I 1 through it is F 12 = µ 0 I 2 2p r I 1 l sin 90° F 12 = µ 0 I 1 I 2 l 2p r (The angle between l and B 2 is 90° and B 2 Is emerging out) F 12 = F 21 = F = µ 0 I 1 I 2 l 2p r F / l = µ 0 I 1 I 2 2p r or or Force per unit length of the conductor is N / m (in magnitude) (in magnitude) x B 1 B 2Read More
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