Magnetic fields

You will be able to

• Calculate the force on a current-carrying conductor using F = BIL sin θ.
• Use Fleming's left-hand rule to predict the direction of the force.
• Determine the magnetic flux density from the gradient of a graph of force against current.

You will be able to

• Calculate the force F = Bqv on a charged particle moving at right angles to a magnetic field, and the radius r = mv / Bq of its circular path.
• Explain how crossed electric and magnetic fields select particles of one speed, v = E / B.
• Use V_H = BI / (ntq) to explain why the Hall voltage is much larger in a semiconductor than in a metal.

You will be able to

• Calculate magnetic flux Φ = BA cos θ and flux linkage NΦ.
• State Faraday's law: the induced e.m.f. equals the rate of change of magnetic flux linkage, e.m.f. = −Δ(NΦ)/Δt.
• Use Lenz's law to predict the direction of an induced current, and explain why the e.m.f. of a rotating coil is greatest when its flux linkage is zero.