Electromagnetic induction Flashcards
What is magnetic flux
The magnetic flux is the product of an area and the component of flux density perpendicular to that area
φ = B x A = BA cosθ
What is magnetic flux linkage
Magnetic flux linkage is defined as the product of the number of turns of the coil and the magnetic flux linking each turn
Φ = Νφ = NBA = NBcosθ
What is Faraday’s Law
It states that the induced e.m.f. in a circuit is directly proportional to the rate of change of magnetic flux-linkage
What is Lenz’s Law
It states that the direction of the induced e.m.f is such that it produces effects to oppose the change causing it.
What is the equation for induced e.m.f.
ε = -(dΦ/dt) or -N(dφ/dt)
Use Faraday’s and Lenz’s Laws to explain EM induction in a conducting rod cutting a field at right angles
- When conductor is moved across magnetic field, magnetic field is cut
- By Faraday’s law, induced e.m.f = rate of change in magnetic flux
- If circuit is closed, an induced current flows in the conductor
- Applying Lenz’s law
- Direction of induced current will be such that it opposed the change causing it
- By using Fleming’s Right Hand rule, an induced current flows in the conductor
- According to Fleming’s Left Hand rule, the conductor will experience a electromagnetic force downwards
What are the steps to answer qualitative questions on EMI
- Identify the change in magnetic flux-linkage
- Using Faraday’s law, deduce emf induced
- Check if circuit closed
- Using Lenz’s Law, state induced current flows in direction to oppose change in magnetic flux
- Find direction of induced emf/current
- Discuss energy conservation
What is the equation for induced current
I = E/R = BLv/R
What is the equation for the induced emf in a homopolar generator
ε = Bπr^2f
- f is the frequency of rotation of disc or revolutions per unit time
What is the equation for induced emf in AC generator
ε = -dΦ/dt = NBAω sinωt = ε. sinωt
-ε.is maximum emf
