Topic 12 🧲🧭 Flashcards
At which part of a magnet are the magnetic forces strongest?
The poles of the magnet
What type of force is exerted if two like poles of a magnet are brought near eachother?
A repulsive, non-contact force
What type of force is exerted if two unlike poles of a magnet are brought near eachother?
An attractive, non-contact force.
What is a magnetic field?
The region surrounding a magnet where another magnet or magnetic material experiences a non-contact force.
What is the difference between a permanent magnet and an induced magnet?
- Permanent magnet produces its own magnetic field.
- Induced magnet becomes magnetic when placed in a magnetic field.
What type of force does induced magnetism always cause?
A force of attraction
What is the effect when an induced magnet is removed from a magnetic field?
The induced magnet loses most/all of its magnetism
Give four examples of magnetic materials.
- Iron
- Steel
- Cobalt
- Nickel
What can always be said about the force between a magnet and a magnetic material?
It is always attractive
In what direction does a magnetic field point?
- In the direction of the force that a North Pole would experience if placed in the field.
- From the north seeking pole to the south seeking pile of a magnetic.
What does a magnetic compass contain?
A small bar magnet that points in the direction of Earths magnetic field
What is produced when current flows through a conducting wire?
A magnetic field is produced around the wire
What determines the strength of the magnetic field around a current carrying wire?
The magnitude of the current flowing through the wire
Does a high concentration of field lines ,Evan the field is strong or weak?
Strong
True or False: magnetic field lines never cross over eachother?
True
How is a plotting compass used to map out a magnetic field?
- Place a compass on a piece of paper near the field.
- Draw an arrow in the direction the compass points.
- Repeat at different points on the paper.
- Join the arrows to make a complete field pattern.
What is a solenoid?
A coil of wire which when current passes through creates a strong magnetic field.
Describe the magnetic field found inside a solenoid.
Strong and uniform
Is the field on the outside of a solenoid strong or weak? Why?
Weak. The fields from each coil cancel out, making the outside field weak.
What is an electromagnet?
- A solenoid with an added iron core.
- Adding the iron core increases the strength of the magnetic field
What is the motor effect?
When a force is exerted between a magnetic field and a current-carrying conductor placed in that field.
What rule is used to determine the force produced by the motor effect?
Fleming’s left hand rule
When using Fleming’s left hand rule what does the forefinger represent?
Points in the direction of the magnetic field
When using Fleming’s left hand rile what does the second finger represent?
Points in the direction of the current flow in the conductor
When using Flemings left hand rule what does the thumb represent?
Points in the direction of the force produced by the motor effect.
What factors affect the size of the force on a current carrying wire in a magnetic field?
- The magnitude of the current flowing through the conductor.
- The strength of the magnetic field that the conductor is placed in.
If the direction of current in a current carrying wire is placed in a uniform magnetic field is reversed, what happens to the force?
The direction of the force is reversed
If the strength of the current in a current carrying wire is placed in a uniform magnetic field is increased what happens to the force?
The strength of the force is increased,
Give the equation linking force, magnetic flux density, current and length.
F = BIL
What criteria must be met for the equation linking force, magnetic flux density, current and length to hold?
The conductor must be at right-angles to the magnetic field it is placed in
What is the unit for magnetic flux density?
Tesla, T
If the current and the magnetic field are parallel to each other, which direction would the force act in?
No force will act
How does an electric motor work?
- A coil of wire, carrying a current, is placed in a magnetic field.
- The forces on the two sides perpendicular to the field experience forces in opposite directions.
- This cause a rotational effect
How are electric motors kept rotating?
A split ring commutator is used. This switches the current direction every half turn, which ensures that the coil keeps spinning.
