magngetism & electromagnetic induction Flashcards
what is a magnet ?
magnet is any object that produces a magnetic field
in a magnetic field diagram, what do denser lines represent?
The density of the lines represent the magnetic field strength. The dense of the lines, the stronger than magnetic field.
Explain the core practical of drawing a magnetic field
A compass always lines up with a magnetic field. When a compass is put near a bar magnet the needle in the compass lines up with its magnetic field, the student then draws a dot where the needle points and moves the magnet to that point. the student then repeats this until they have drawn a magnetic field diagram of the magnetic field, going from the north pole to the south pole.
why when you put North Pole and a north pole together do they repel?
Since the magnetic field always goes from the north pole to the south pole, when a north pole and north pole is put together, the magnetic field collides and causes repulsion of
either magnet.
What is a magnetic material?
Magnetic material is any object that can be influenced by magnetic fields and has the potential to become a magnet
what are four common magnetic elements
Nickel
Iron
Cobalt
Steel
what is a permanent magnet?
A permanent magnet is a object that has a magnetic field at all times
Give two examples of a permanent magnet
The Earth
A bar magnet.
What is an induced magnet?
An induced magnet only has a magnetic field temporarily
When is an induced magnet formed?
When put in the presence of a permanent magnet
what is the relationship between a permanent magnet and an induced magnet?
They always have a force of attraction between them no matter what
what is a magnetically soft material?
A material that loses its magnetism quickly
What is a magnetically hard material?
A material that loses its magnetism slowly
what is an electromagnetism?
The phenomenon whereby an electric current produces their own magnetic field
Describe the right hand rule for current direction and magnetic field direction
The right hand rule where forming a thumbs up, represents the direction of magnetic field and current. The thumb represents the direction of the current and the curvature of the fingers represents the magnetic field. To find the direction of the magnetic field. You simply point your thumb in the direction of the current.
in a circular coil ellipsis occurs. What is this?
in a circular coil, the two magnetic fields going around the coil join together to form another magnetic field going directly down the middle. This is called ellipsis.
What is a solenoid?
A solenoid is a wire formed into multiple circular coils
Why is a solenoid an electromagnet?
A solenoids and an electromagnet, because the magnetic field is the same as that of a bar magnet. It has a north pole and a south pole and the direction of the magnetic field goes from north to south.
What are the four ways of increasing the electromagnetic strength in a solenoid?
- increased current
2.increased number of coils - decreased length, but the same number of coils
- Adding an iron core (induced magnet).
what is the motor effect?
A current carrying wire in the presence of a magnetic field, will experience a force
when does the wire with a magnetic field experience full force when in the presence of another magnetic field?
When at 90° angle to the magnetic field
when will the wire with a magnetic field experience no force when in the presence of another magnetic field.
When the wire is going in the same direction as the magnetic field
describe Flemings, left-hand rule
flemings left-hand rule, describes the force and the direction of the force in which an object is pushed when, in the presence of a magnetic field, whilst that object has a magnetic field of its own. In Flemmings left-hand roll, the thumb is facing upward. The index finger is facing in an adjacent angle to the thumb and the middle finger is facing towards you. The thumb represents the direction of the force. The index finger represents the direction of the magnetic field. The middle finger represents the direction of the current.
What is the equation to work out The strength of the force applied to an object due to the motor effect
Force = magnetic flux density x current x length of wire
What is the units for magnetic flux density?
Tesla
what are the units for current?
Amps
What is the unit for the length of the wire?
Metres
because of Flemmings, left-hand rule, when two wires are connected together, what happens to the wire in a magnetic field?
The wire turns 180° and the direction of the forces swap
how do you turn The joint wire in a magnetic field 360°
To turn the joint wire, 360°. You have to add a split ring commutator.
what is the role of a split ring commutator?
The split ring commutator swaps the positive and negative connections every half turn which changes the direction of current every half turn.
this allows the joint wire to spin 360° over and over until the current is taken away
What ways can we increase the speed of the joint wires in a magnetic field?
. Increase the speed.
. Add more turns to the coils.
. Use a stronger magnet.
What is electromagnetic induction?
electromagnetic induction is moving, a coil up and down when wrapped around a magnetic field to induce a potential difference (voltage)
what in terms of potential difference happens when a change in direction occurs between a magnetic field?
When the direction is changed, the potential difference swaps. if the coil is closed and makes a circuit, then the current created changes direction.
What three ways are there to change the size of the induced potential difference or current?
. Change strength in magnet
. Move the wire quicker
. Create more turns on the coil.
why in electromagnetic induction does the potential difference disappear when the wire stops moving?
Because the potential difference occurs when a change in magnetic field occurs. Therefore, when the wire stops moving there is no change in magnetic fields and therefore no potential difference and therefore no current
what is a transformer?
A transformer is used to increase or decrease a potential difference
explain the process of how a transformer works
An alternating potential difference passes through the primary coil. Since this is a closed circuit, this potential difference causes a current to flow which is also alternating and therefore causes an alternating magnetic field around the primary coil. Since the iron core is a magnetic material, the magnetic field around the coil causes this iron to become an induced magnet. Because of the magnetic field around the iron core, the secondary coil induces a potential difference and causes a current to flow.
what is a step up transformer?
A step up transformer has more coils on its secondary coil to increases the input potential difference
what is a step down transformer
A step down transformer has less coils on the secondary coil to decrease the input potential difference
State the two equations used to work out the final potential difference or current on the secondary coil.
Vp / Vs = Np / Ns
Vp x Ip = Vs x Is
