4.6 Electromagnetic Effects Flashcards
when is EMF induced in a coil
when a bar of magnet is pushed is pushed in and out of it
how are EMFs of opposite signs produced
by EMFs in opposite directions
factors affecting EMF induction
1- moving the wire/coil faster
2- stronger magnet
3- adding more turns to the coil
alternating current (a.c.)
continuously changes direction
eg, electricity
direct current (d.c.)
constantly going the same way (positive-negative)
eg, batteries
slip rings
an attachment at the end of the coil, which transfers the current to metal brushes, while allowing the coil to rotate freely
transformers
electrical device that is used to increase or decrease the voltage of alternating current
what does a transformer consist of
two coils wrapped around a soft iron core
step-up transformer
- increases the voltage of power source
- turns on secondary coil more than primary coil
step-down transformer
- decreases the voltage of power source
- turns on primary coil more than secondary coil
how is electricity transmitted
1- step-up transformers increase the voltage
*before transmissions
2- step-down transformers decrease the voltage
*before reaching destination
how does high voltage reduce power loss
- current heats up in wires at large distances causing power loss
- raising the voltage can transmit the same amount of power with less current, so less power loss
direction of a magnetic field length
The direction of the force on the north pole of a magnet placed at that point
factors effecting the strength and direction of a magnetic field around a current wire
- If the current is increased, the field will get stronger
- If the direction of the current is changed, the direction of the field will change
