Electromagnetic Induction

HideShow resource information
  • Created by: LZ95
  • Created on: 17-04-14 21:31
What is electromagnetic induction?
When a wire cuts across the lines of a magnetic field, causing an induced emf
1 of 29
What is the induced emf increased by?
Moving the wire faster, using a stronger magnet and making the wire into a coil
2 of 29
In which two situations does the emf become 0?
1. When the wire is parallel to the field lines 2. When the motion between the wire + magnet stops
3 of 29
When a road with free electrons is passed through a magnetic field, what happens to the electrons?
They are moved to one end of the rod, away from the other end, by the magnetic force.
4 of 29
When working out the direction of the force in this situation, which rule would you use?
Fleming's right hand rule
5 of 29
What does the rate of transfer of energy from the source of emf to other components equal to?
Product of induced emf and current
6 of 29
What is Faraday's law?
Induced emf in a circuit = rate of change of flux linkage through the circuit
7 of 29
What must the relationship be between the applied and magnetic force to keep a conductor moving through the field?
Applied force must be equal and opposite to magnetic force.
8 of 29
Which way does the current pass in a North Pole?
Anticlockwise
9 of 29
Which way does the current pass in a South Pole?
Clockwise
10 of 29
What is Lenz's law?
Direction of the induced current is always such as to oppose the change that caused the current.
11 of 29
What is the unit for magnetic flux?
Weber (Wb)
12 of 29
Name 4 ways in which peak emf can be increased
Increasing the speed, using a stronger magnet, using a larger coil and increasing the no. of turns of coil
13 of 29
Why is the induced emf referred to as the 'back emf'?
As it acts against p.d.
14 of 29
What are the emf and current like at low speed?
Current = high, emf = low
15 of 29
What are the emf and current like at high speed?
emf = high, current = low
16 of 29
What is a typical A.C. generator?
A rectangular coil spinning in a uniform magnetic field.
17 of 29
When is the max emf achieved?
When the sides of the coil cut at right angles along the field lines
18 of 29
What does a transformer do?
Changes an alternating p.d. to a different peak value
19 of 29
What does a transformer consist of?
A primary and a secondary coil, wrapped around the same iron core.
20 of 29
What happens when the primary coil is connected to a source of alternating p.d.?
Alternating magnetic field is produced in the core, passing through the secondary coil.
21 of 29
What does the changing magnetic field produce in the secondary coil?
An alternating emf
22 of 29
What are the properties of a step up transformer?
Voltage is stepped up and current is stepped down, as there are more turns on the secondary coil
23 of 29
What are the properties of a step down transformer?
Voltage is stepped down and current is stepped up, as there are more turns on the primary coil
24 of 29
Name 3 ways in which a transformer can be made more efficient
Low resistance windings, laminated core and soft iron core
25 of 29
How do low resistance windings improve efficiency?
They reduce the power wasted due to the heating effect of the current
26 of 29
How does a laminated core improve efficiency?
Induced currents (eddy currents) reduced so magnetic flux is as high as possible.
27 of 29
How does a soft iron core improve efficiency?
It is easily magnetised + demagnetised which reduces the power wasted in repeated magnetisation + demagnetisation of the core
28 of 29
At what frequency and voltage does the national grid generate A.C.?
50Hz and 25kV
29 of 29

Other cards in this set

Card 2

Front

What is the induced emf increased by?

Back

Moving the wire faster, using a stronger magnet and making the wire into a coil

Card 3

Front

In which two situations does the emf become 0?

Back

Preview of the front of card 3

Card 4

Front

When a road with free electrons is passed through a magnetic field, what happens to the electrons?

Back

Preview of the front of card 4

Card 5

Front

When working out the direction of the force in this situation, which rule would you use?

Back

Preview of the front of card 5
View more cards

Comments

ravioli

This is great thank you so much!

Similar Physics resources:

See all Physics resources »See all Electromagnetic Induction resources »