Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Magnetic field inside a solenoidSlide 10Slide 11Slide 12Applications of MagnetismMagnetic ForceTorque on a Current Loop DC motorSlide 16A current generates magnetic fieldA current generates magnetic fieldMagnetic field generated by Magnetic field generated by B=oI/2rIr×BBrI>><<>B=oI/2rA long, straight current A current loopNSA long straight vertical segment of wire traverses a magnetic field of magnitude 2.0 T in the direction shown in the diagram. The length of the wire that lies in the magnetic field is 0.060 m. When the switch is closed, a current of 4.0 A flows through the wire from point P to point Q.1. Which one of the following statements concerning the effect of the magnetic force on the wire is true?(a) The wire will be pushed to the left.(b) The wire will be pushed to the right.(c) The wire will have no net force acting on it.(d) The wire will be pushed downward, into the plane of the screen.(e) The wire will be pushed upward, out of the plane of the screen.2. What is the magnitude of the magnetic force acting on the wire?(a) 0.12 N (c) 0.48 N (e) 0 N(b) 0.24 N (d) 67 NXXA loop of wire with a weight of 1.47 N is oriented vertically and carries a current I = 1.75 A. A segment of the wire passes through a magnetic field directed into the plane of the page as shown. The net force on the wire is measured using a balance and found to be zero. What is the magnitude of the magnetic field?(a) zero tesla (d) 1.5 T(b) 0.51 T (e) 4.2 T(c) 0.84 TXTwo loops carry equal currents I in the same direction. The loops are held in the positions shown in the figure and are then released. Which one of the following statements correctly describes the subsequent behavior of the loops?(a) Both loops move to the left.(b) The loops remain in the positions shown.(c) The top loop moves to the right; the bottom loopmoves to the right.(d) The loops repel each other.(e) The loops attract each other.XTwo long, straight, parallel wires separated by a distance d carry currents in opposite directions as shown in the figure. The bottom wire carries a current of 6.0 A. Point C is at the midpoint between the wires and point O is a distance 0.50d below the 6-A wire as suggested in the figure. The total magnetic field at point O is zero tesla.1. Determine the value of the current, I, in the top wire.(a) 2 A (c) 6 A (e) This cannot be determined since(b) 3 A (d) 18 A the value of d is not specified.X2. Determine the magnitude of the magnetic field at point C if d = 0.10 m.(a) 2.4x10–5 T (c) 9.6x10–5 T (e) 1.4x10–4 T(b) 4.8x10–5 T (d) 1.1x10–4 TXTwo long, straight wires are perpendicular to the plane of the paper as shown in the drawing. Each wire carries a current of magnitude I. The currents are directed out of the paper toward you. Which one of the following expressions correctly gives the magnitude of the total magnetic field at the origin of the x,y coordinate system?a) oI/2d (b) oI/2d (c) oI/2d (d) oI/2d (e) oI/dXThe radius of a coil of wire with N turns is r = 0.22 m. A current Icoil = 2.0 A flows clockwise in the coil, as shown. A long, straight wire carrying a current Iwire = 31 A toward the left is located 0.05 m from the edge of the coil. The magnetic field at the center of the coil is zero tesla. Determine N, the number of turns.(a) 2 (b) 4(c) 3(d) 1(e) 6XMagnetic field inside a solenoidMagnetic field inside a solenoid B=NoI/l=noI where N is number of loops or turns, l the length of the solenoid, and n the number of the loops per unit lengthBitter Disk Florida-Bitter Disk““Loops” for Real MagnetsLoops” for Real MagnetsB=noI The larger I, the stronger BB=noI The larger n, the stronger BThe strongest field is The strongest field is 45 T, more than a 45 T, more than a million times stronger million times stronger than the earth’s field, than the earth’s field, 33××1010-5-5 T TExample: A solenoid 20 cm long and 4 cm in diameter is wounded with a total of 200 turns of wire. The solenoid is aligned with its axis parallel to the earth’s magnetic field which is 3x10-5 T in magnitude. What should the current in the solenoid be in order for its field to exactly cancel the earth’s field inside the solenoid? Solution: Since l=0.2 m and N=200 turns, B=NoI/l I=Bl/oN=(3x10-5T)(0.2)/(4x10-7Tm/A)(200)=0.024 A=24 mAThe solenoid diameter has no significance except as a check that the solenoid is long relative to its diameter.Applications of MagnetismApplications of MagnetismMagnetic ForceF=Bqvsin for a moving charge F=BIlsin for a currentTorque on a Current LoopDC motorF=IbB=F×r Top viewTop viewBIIו@&a/2a/2brFFSide viewSide viewFB&@Loop plane makes an angle Loop plane makes an angle with B with B=IBAsinbecause a2sinSide viewSide viewFFB&@Loop plane || BLoop plane || B=Fa/2 + Fa/2 = Fa=IbBa=IBA where A=ab, the area of the loopSide viewSide viewFFB&@Loop plane makes an angle Loop plane makes an angle with B with
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