magnetism and electromagnetism Flashcards
When an electric current flows in a wire it creates a _______ around the wire
When an electric current flows in a wire it creates a magnetic field
how does winding the wire into a coil strengthen magnetic field?
by concentrating the field lines
how to make an electromagnet?
wrap a current carrying coil around a soft magnet like iron
how to increase strength of an electromagnet?
add more turns to the coil
increase current flowing through wire
how to reverse magnetic field of an electromagnet?
The magnetic field around an electromagnet has the same shape as the one around a bar magnet
The field can be reversed by reversing the direction of the current
magnetic field around current carrying wire is what shape?
concentric circles
why must a wire be thick?
to prevent heat loss, overheating
to prevent wire from sagging, bending or melting
to reduce resistance
how to reduce force on wire in motor effect?
use less powerful magnet or make the distance greater
reduce current flowing through wire
in motor effect, what are the three ways we can make the coil spin in an opposite direction?
- reverse current
-reverse cell terminal - reverse magnetic poles
what is the role of split ring commutator?
- it is what allows coil to keep turning
-current in commutator changes the direction every half a turn
what is the role of carbon brush in motor?
current supplied to coil through this brush
what would happen if there was no commutator in motor?
coil would only make a half turn and go back, wouldnt spin whole turn
what is the assumed resistamce of batteries, ammeters, voltmeters?
zero
why do voltmeters have extremely high resistences?
in order to prevent current from passing through them
define current
rate of flow of negatively charged electrons
define voltage
Voltage is the energy transferred per unit charge passing between two points.
what is 1 volt equivalent to?
1 volt is equivalent to the transfer of 1 joule of energy by 1 coulomb of charge, or 1 V = 1 J/C.
True or False?
When electrons flow in a circuit, they lose energy
True
it gets transferred to wires and components
