Revision topic 15 Flashcards
what is the magnetic compass
it is a compass with a tiny magnetic nedel pivoted at its center, and since the earth, the magnetic field is concentrated at the magnetic north and south pole allows one end of the compass is pointing north and the other pointed south
what can be magnetized
iron and steel, and all ferrous material and some nonferrous material like cobalt and nickel.
what is a magnetic field
the space around the magnet
what happens to the magnetic field lines
lines in a bar magnet would curve from the north pole to the south pole
what happens in induced magnetism
unmagnetized magnet material can be magnetized by placing it in a magnetic field inducing it
explain how iron can be induced
when you place an iron in a magnetic field the rod poles closest with the magnet poles would become an opposite polarity making an attraction between the iron rod and the magnet, and if you remove iron from the magnetic field it would lose all its magnetism
in a uniform field, the lines of the magnetic field are
parallel to each other
when an electrical current passes along a wire what will happen
a magnetic field around the wire is set up, which can be seen by iron filling, the magnetic field would be strongest near the wire, and if we reverse the current the direction of the magnetic field would be reversed
how can you set up and prove that a magnetic field is stronger near the wire and that when the current is reversed the direction is reversed
take a battery, a wire, and a wooden stand (eliminate magnetism caused by a near object like iron), and a current carrying wire, a plotting compass, and a paper, so take a paper and hang it on the wooden stand perpendicularly then take a current carry wire and place it through the paper and connect it with a wire going through it that is connected to a battery
to prove that reversing the current reverse the direction:
you would take a compass and place it on the paper and turn on the current and see how the arrow moves then reverse the current and you would see the arrow move in the opposite way
to prove that the magnetic field gets stronger when we are closer to it:
take a compass and start moving away from the magnetic field after you move away from enough the compasses arrow would point at the north (earth natural magnet)
the magnetic field lines around the wire
are in circles centered on the wire in a plane perpendicular to the wire
what is a solenoid
it is a long coil of insulated wire
what happens when an electrical current passes through a solenoid
a magnetic field would appear around it, that would be stronger and more uniformed inside the solenoid, and its direction would be reversed if the current is reversed, and it increases in strength if the current increases
what are electromagnet made up from
they are made up of insulated wires around an iron bar, so when the current passes through the iron would be magnetized
electromagnets are used in
- the scrapyard crane
- an electrical bell
- the relay
what is the motor effect
it is when an electrical motor works because the force can act on a wire in a magnetic field while a current is passing through the wire
the size of the force in a motor effect can be increased by
- increasing the current
2. and using a stronger magnet
in the motor effect, what does the size of the force depend on
the angle between the wires and the magnetic field, as the force, is at its strongest when the wire is perpendicular to a magnetic field, and it’s at its zero if it was parallel to the magnetic field
in motor affect the direction of the force is always
at right angles with the wires and the field lines, and the direction would be reversed if the current was reversed
how can you use fleming righthand to determine where everything is
the first finger = the magnetic field
the second finger = the moment of the current
the third finger = the movement of the force
what does a simple motor consist of and how does it work
it consists of a rectangular coil made of insulated wire that is connected to the battery via graphite brushes that press against a metal split-ring commutator
so when a current passes through the coil would spin because a force would act on each side of the coil due to the motor and the force of one side acts in the opposite direction of the other side, the split ring commutator would reverse the current passing through the wire at every half-turn of the coil, because of this the current of the half beside each pole in that magnet would remain in the same direction making the coil remain in the same direction
explain how a loudspeaker would constantly make the diaphragm vibrate
when the current moves through the coil it would be forced to move because of the motor effect, so each time the current changes its directions the force reverses its direction so the coil would repeatedly go back and forth and this moment would cause the diaphragm to vibrate so that sound waves are created
what does generate contain
a coil of wires that spin in a magnetic field
what is electromagnetism induction
it is the process where the potential difference is induced across the end of the wire when it cuts across a magnetic field
how can we test for the generator effect
we would set up an insulated wire to an ammeter then take the wire to move it between the poles in the u-shaped magnet and observe the ammeter, you would discover that the pointer would deflect as the current is generated when the wire cuts across the magnetic field. this is because the potential is induced in the wire when it cuts the magnetic field, this effect is called the generator effect