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CAIE
20. Magnetic fields
20.1 Concept of a magnetic field
- understand that a magnetic field is an example of a field of force produced either by moving charges or by permanent magnets
- represent a magnetic field by field lines
20.2 Force on a current-carrying conductor
- understand that a force might act on a current-carrying conductor placed in a magnetic field
- recall and use the equation F = BIL sin θ, with directions as interpreted by Fleming’s left-hand rule
- define magnetic flux density as the force acting per unit current per unit length on a wire placed at rightangles to the magnetic field
20.3 Force on a moving charge
- determine the direction of the force on a charge moving in a magnetic field
- recall and use F = BQv sin θ
- understand the origin of the Hall voltage and derive and use the expression VH = BI /(ntq), where t = thickness
- understand the use of a Hall probe to measure magnetic flux density
- describe the motion of a charged particle moving in a uniform magnetic field perpendicular to the direction of motion of the particle
- explain how electric and magnetic fields can be used in velocity selection
20.4 Magnetic fields due to currents
- sketch magnetic field patterns due to the currents in a long straight wire, a flat circular coil and a long solenoid
- understand that the magnetic field due to the current in a solenoid is increased by a ferrous core
- explain the origin of the forces between current-carrying conductors and determine the direction of the forces
20.5 Electromagnetic induction
- define magnetic flux as the product of the magnetic flux density and the cross-sectional area perpendicular to the direction of the magnetic flux density
- recall and use Φ = BA
- understand and use the concept of magnetic flux linkage
- understand and explain experiments that demonstrate
- recall and use Faraday’s and Lenz’s laws of electromagnetic induction