Electromagnetic induction Flashcards
Electromagnetic induction
Occurs whenever a wire cuts across the lines of a magnetic field. If the wire is part of a complete circuit, the induced emf forces electrons round the circuit.
Current at the north pole end of a solenoid
Passes anticlockwise.
Current at the south pole end of a solenoid
Passes clockwise.
Lenz’s law
The direction of the induced current is always such as to oppose the change that causes the current.
Magnetic flux, Φ, equation
Φ = BA
Unit of magnetic flux, Φ
Weber (Wb), equal to 1 T m^2
Magnetic flux linkage through a coil of N turns
= NΦ = NBA
Faraday’s law of electromagnetic induction
The induced emf in a circuit is equal to the rate of change of flux linkage through the circuit.
Induced emf equation
ϵ = - N ΔΦ/Δt
Root mean sqaure AC value definition
The value of direct current that would give the same heating effect as the AC in the same resistor.
I rms
I rms = 1/
I rms
I rms = 1/√2 Io
V rms
V rms = 1/√2 Vo
Transformer rule
Vs/Vp = Ns/Np = Ip/Is
Step up transformer
Has more turns on the secondary coil and hence secondary voltage is stepped up from primary voltage.
Step down transformer
Has less turns on the secondary coil and hence secondary voltage is stepped down from primary voltage.
Efficiency of a transformer equation
IsVs/IpVP x 100%
