15 Electromagnetic Induction Flashcards
Voltage is induced in a conductor or a coil when
It moves through a magnetic field or when a magnetic field changes through it
Factors that affect size of voltage induced
- speed of wire
- number of turns
- size of coils
- strength of magnetic field
Describe the generation of electricity by rotation of magnet within a coil
- coil is rotated within a magnetic field
- wire cuts the magnetic field line
- this induces a voltage in coil
Transformers changes size of an alternating voltage by
Having different numbers of turns on the input and output sides
Structure of transformer
- alternating current in the primary coil produces a changing magnetic field around the primary coil
- the iron core channels the changing field through the secondary coil
- the changing magnetic field induces a voltage in the secondary coil
If there are more coils in the secondary
Voltage increases (step up)
Because power is conserved and p=iv current decreases
If there are more coils in a primary
Voltage decreases (step down)
Current increases
Step up transformers increase voltage as there’s
More secondary turns than primary
Step down transformers decrease voltage as theres
More primary turns than secondary
Input (primary) voltage / output (secondary) voltage =
Primary turns / secondary turns
For 100% efficiency
Input power = output power
Primary voltage x primary current = secondary voltage x secondary current
For 100% efficiency
Input power = output power
How to step up transformed makes network efficient
- increase potential difference
- current is decreased in wire
- less current in wire —> less electrons flowing per second
- less thermal energy dissipated (heat loss) to surroundings
If a wire cuts a changing magnetic field
An alternating voltage is induced across wire
Step down transformers lower voltage to make it
Safe to use
Power station voltage
25kV
Household voltage
230V
