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10th CLASSES PHYSICS DAILY PLAN 8) Magnetic force between two current-carrying wires: SUBJECT: Force on current carrying conductor and B1 I1 charged particle AIM: to determine force on a current carrying conductor and torque on a current carrying loop DURATION: 160min REAL LIFE: galvanometer,el.motor. PRESENTATION: F d F B2 I2 L [Parallel currents having the same direction attract each other] I B B I=0 B B1 I2 B2 F I Right hand rule-2: B :: Fingers I :: Thumb F :: Inside the hand F [Parallel currents having opposite directions repel each other] [Note: F = F even if the currents are different. This is because of the third law] Magnitude of force: Formula: F=I1 L B2 μ I μ I I F= I1 L ( 0 2 ) F = 0 1 2 L 2π d 2π d I L I1 F=I L B B F μ I I F = 0 1 2 L 2 d or Ex: Find net force on the loop. Ex: Find net force on I3. I2 General formula: I I1 I1 I2 I3 L L F L B L d x x L 9) Torque on current loop: F=I L B F = I (L Sin) B Note: is between B and I. Class activity: Hold two pens ends together in different orientations and show that they always determine a plane unless they are parallel. Place a third pen perpendicular to them as the force vector. Ex: ..F = I L B Sin F F I S N I B F B I=5A Torque= 2 F a 2a 2Wb/m2 10 cm = 2 (I L B) a = I B (2aL) Find F=? I I F F 127° 1.2 T Ex: What is the force on the wire? (Sin 45°=0.707) L = I B (Area). 4A 20 cm 45° Side view: F a I a I F = 2 F a y Ex: Find direction of F or B B a a F I B v + a Sin v B + = 2 F a = 2 F a Sin I F F v Trajectory of particle: Since F is always perpendicular to v, the charge will perform circular motionwith constant speed. = I B (Area) Sin ( is between B and Normal) [So torque is zero when normal is parallel to B] Applications: A) Galvanometer: Used to measure small currents v B + v F + F F N S I I spring B) Electric motor: Class activity: Showing a real electric motor and describing how current changes direction when torque becomes zero. 10) Force acting on a charge moving in magnetic field: [Force on current is sum of magnetic forces on moving charges in the wire] F F v + F F + v F v + + v [Magnitude of this force is proportional to magnitudes of charge, magnetic field and velocity] q Right hand rule for (+) charge: (Hand stretched) B + + r= Fc = m ac v mv qB q v B = m v2 / r Ex: Electrons having 107 m/s velocity are shot into magnetic field of 8 x 10-4 T. Find radius of trajectory. (me = 9 x 10-31kg, e = 1.6 x 10-19 C) Ex: a) Determine of charges. b) Find q1/q2=? masses of particles are sign q2 if 2 v When a charge moves in magnetic filed, cutting the field lines, there is a magnetic force on the charge. F r v + v + Finding radius: Voltmeters and ampermeters are produced by connecting a galvanometer with a resistance in series or parallel. B + r F v B q1 v equal. B Ex: q + m B 2v m + Compare the period of revolution for two identical particles. q v v q B ::: Fingers v ::: Thumb F ::: Inside the hand v Sol: Periods are equal: F + Magnitude of force: 2v B F = q v B 2r + v r General formula: B q + F = q v B v v F = q (v Sin) B v F = q v B Sin is between B and v... F Rule: There can be any angle between v and B. But F is always perpendicular to both v and B. v HOMEWORK: 23-24-26-27-28-34-35 MULTIMEDIA: Basic 48,Cerway 3,Akademedia DEMONSTRATION: mag.force on a cond. EXPERIMENT: TEACHER: DIRECTOR: B