Faraday's Law, Lenz's Law and Alternating Currents Flashcards
What is an induced emf?
An induced emf is directly proportional to the rate of change of flux linkage
Faraday’s Law
Magnitude of emf = N(change in magnetic flux)/time
Induced EMF for conducting rod
BLv
Lenz’s Law
The induced emf is always in such a direction as to oppose the change that caused in
Equation for Induced EMF in a rotating coil
NBAwsin(wt)
Equation for Flux Linkage in a rotating coil
NBAcos(wt)
How to find Voltage RMS
Vpeak/sqrt2
Current rms
Currentpeak/sqrt2
Ohm’s Law
V = IR
Equation for Powe
IV
Ideal Transformer Equation
Vp/Np = Vs/Ns
How to identify a Step-Up Transformer?
Np<Ns then Vp<Vs
Voltage across secondary coil is larger
How to identify a Step-Down transformer?
Ns<Np then Vs<Vp
Voltage across secondary coil is smaller
What is an ideal transformer
A transformer where there is no energy loss
How can energy be lost in a transformer?
Due to heat in the primary and secondary coils
Energy to magnetise the iron core
How to prevent energy loss?
Use thick copper wire with less resistance
Use magnetically ‘soft’ material, which means not much energy needed to magnetise or demagnetise core
Reducing Eddy Currents
Use laminated cores - made up of strips of iron glued together
How to calculate transformer efficiency
Pout/Pin or IsVs/IpVp
Equation for Power
E/T
