b fields
- Created by: Anwen
- Created on: 22-05-14 22:35
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- B-fields
- Magnetic field lines
- always move N -> S
- When two oppose there is a neutral point usually denoted by X
- Flemming L.H.R
- thumb=Motion First=Field second=Current
- Flux Linkage = If the coil in the magnetic flux consists of N turns the flux linkage is given by N@ (@=thi) unit=WB(webber)
- F=BIlsinO
- Force on a straight wire carrying a current. If a current I flows in a length l of a wire at right angles to a magnetic field of flux density B(it's magnetic field strength)
- F=BIl B=F/Il
- Force on a straight wire carrying a current. If a current I flows in a length l of a wire at right angles to a magnetic field of flux density B(it's magnetic field strength)
- Flux density = the distance between two lines of the field (shorter distance greater density)
- Equations used to calculate flux density
- B= (UoI) ________ 2(pie)a
- Equations used to calculate flux density
- Mgnetic Flux = BAsinO unit=webber D= if a single turn coil of wire encloses an area A and a magnetic Field B makes an angle O with the normal to the plane of the coil, the magnetic flux through the coil is given by @=ABcosO or @=ABsinO
- Relative permeability Ur = B/Bo usually from 1->300 for ferromagnetic material Ur is large and positive
- The Ampere
- To derive an expression for the force, two long straight parallel conductors at a distance 'a' apart in air carrying current I1 and I2 respectively as shown in the diagram -------->
- B1= (Uo*I*1) _____________ 2*(pie)*a
- F=B1*I2*L
- F= Uo*I1*I2*l ______________ 2*(pie)*a
- Wire 1 exerts a force on wire 2 and wire 2 exerts an equal and opposite force on wire 1
- I1=I2=1A l=a=1m subin F= Uo*I1*I2*l ___________ 2*(pie)*a
- Uo = 4(pie)x10-7 Hm^-1
- I1=I2=1A l=a=1m subin F= Uo*I1*I2*l ___________ 2*(pie)*a
- Wire 1 exerts a force on wire 2 and wire 2 exerts an equal and opposite force on wire 1
- F= Uo*I1*I2*l ______________ 2*(pie)*a
- F=B1*I2*L
- B1= (Uo*I*1) _____________ 2*(pie)*a
- D= the ampere is that current which when flowing through 2 infinite thin wires one metre apart in vacuum produces a force between the wires of exactly 2x10-7N per m of length (A)
- To derive an expression for the force, two long straight parallel conductors at a distance 'a' apart in air carrying current I1 and I2 respectively as shown in the diagram -------->
- Force in a changing magnetic field
- V=L/t
- I=nq/t
- t=L/v
- I=nqv/L
- F=BIL =B{nq/L}*L =Bnqv singlecharge = F=Bqv Forelectrons = F=Bev
- I=nqv/L
- t=L/v
- I=nq/t
- V=L/t
- How to increase the field strength within a solenoid
- filling the core with a ferrous metal e.g iron cobalt and nickel
- B=UrUonI
- The magnetic field outside the solenoid and the self inductance of the solenoid are increased in the same proportion.
- filling the core with a ferrous metal e.g iron cobalt and nickel
- Hall Voltage
- DWhen a magnetic field B is applied to a conductor carrying current I at right angles to the field direction a so-called Hall volatage appears across the specimen at right angles to the B and I directions (L.H.R.)
- Vh.prop.B Vh=BI/nxq
- B=magnetic field strength I=cuurent n=numberof charge carryers
- Vh =Bvd d=distance between bottom and top.
- B=magnetic field strength I=cuurent n=numberof charge carryers
- The electrons move into the hall probe, and move in the opposite direction to thwe motion ~(LHR)~ when bottom layer is fullyaturated the electrons pass straight through the probe un deflected
- Cyclotrons, Synchrotrons and Linear accelerators
- Cyclotron
- The charged particles are accelerated in a circular path where the magnetic field is constant. Whilst the radius of the curved path changes (in a swirly pattern) the particles are accelerated by applying a PD across the gap.
- Synchrotrons
- The charged particles are also accelerated in a circular path. However the radius of the path followed by the particle remains constant whilst the applied magnetic field changes.
- Most of the worlds famous particle accelerators e.g CERN in switzerland use the synchrotron technique they reach about 99% the speed of light.
- Advantages = It's possible to accelerate the particles to higher speeds. Higher energy means more energy and smaller waves and therefore the discovery of v. small particles e.g quarks
- Disadvantages it's not possible to accelerate a continuous stream of particles. The particles are accelerated in small bunches then clear the machine before inserting the next bunch. (short burst of particles)
- Advantages = It's possible to accelerate the particles to higher speeds. Higher energy means more energy and smaller waves and therefore the discovery of v. small particles e.g quarks
- Disadvantages it's not possible to accelerate a continuous stream of particles. The particles are accelerated in small bunches then clear the machine before inserting the next bunch. (short burst of particles)
- Most of the worlds famous particle accelerators e.g CERN in switzerland use the synchrotron technique they reach about 99% the speed of light.
- The charged particles are also accelerated in a circular path. However the radius of the path followed by the particle remains constant whilst the applied magnetic field changes.
- Linear accelerators
- The future lies in the linear accelerators which accelerate particles in a straight line. The advantage being that they need less energy to operate because the particle don't expierience centripedal force / accleleration
- Cyclotron
- Centrapedal Force +acceleration
- F= mv^2 __________ r
- F=Bqv
- F=ma
- a=w^2r
- v=rw
- v^2=w^2r^2
- a= v^2/r
- Bqv= mv^2/r
- Bq = mv/r
- for electrons Be=mv/r
- Bq = mv/r
- Bqv= mv^2/r
- a= v^2/r
- v^2=w^2r^2
- v=rw
- a=w^2r
- F=ma
- F=Bqv
- F= mv^2 __________ r
- Force between two wires carrying current
- current in the same direction attract each other (pushed together by a stronger outer field)
- If currents are in opposite direction then the wires repel each other (the strong central magnetic field pushes the wires apart)
- Deflection of charged particles
- Beta goes toward the positive in an electric field and alpha moves towards the negative(muchslower wvelocity than beta)
- Ina magnetic field the alpha particle moves up
- Beta goes toward the positive in an electric field and alpha moves towards the negative(muchslower wvelocity than beta)
- Magnetic field lines
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