Induction Laws and alternators

Question 1

What is Farday’s Law?

Answer 1

• the induced emf is directly proportional to the flux linkage
• ε = N ΔΦ / Δt

Question 2

In a graph of flux linkage against time, what is the gradient?

In a graph of magnitude of emf against time, what is the area under the curve?

Answer 2

• gradient
  
  • size of emf
  • if the line is flat, gradient is 0 and no emf is induced
• 2)
  
  • area under curve is flux linkage change

Question 3

What is Lenz’s Law?

Answer 3

• induced emf is always in such a direction as to oppose the change that cause it

Question 4

How are Lenz’s and Faradays Law combines?

Answer 4

• ε = - N ΔΦ / Δt
• • flux linkage change / time taken

Question 5

Why is a minus used in the combined equation

Answer 5

• shows the direction of the induced emf

Question 6

How is Lenz’s Law basically conservation of energy?

Answer 6

• energy used to pull a conductor through a magnetic field, against the resistance caused by magnetic attract, is what produces the induced current

Question 7

How can Lenz’s law be used to find the direction of an induced emf and current in a conductor travelling at right angles to a magnetic field

Answer 7

Question 8

What is an alternator?

Answer 8

• generator of alternating current

Question 9

What is a dynamo?

Answer 9

• i.e. generator
• conver KE to electrical nergy - induce an electric current by rotating a coil in a magnetic field

Question 10

How is an alternating current produced by a dynamo?

Answer 10

• output voltage and current change direction with every half rotation of coil

Question 11

Answer 11

• Induced current such as to opposes the change producing it
• Switch on - current increases the flux through Y
• Current opposite direction/anticlockwise to create opposing flux
• Switch off - flux thorough Y due to X decreases so current travels clockwise to create flux to oppose the decrease