What are the two poles of a magnet?
North (north seeking) and South (south seeking).
Define a magnetic field.
A region where other magnets or magnetic materials (iron, steel, nickel, and cobalt) experience a non-contact force.
In which direction do magnetic field lines always point?
From North to South.
How can you tell where a magnetic field is the strongest by looking at field lines?
The closer together the lines are, the stronger the magnetic field. They are closest at the poles.
What type of force exists between a magnet and a magnetic material?
It is always attractive, regardless of which pole is used.
What is the rule for magnetic poles interacting with each other?
Like poles (N-N or S-S) repel; Unlike poles (N-S) attract.
What is inside a compass that allows it to work?
A tiny bar magnet. Its north pole points in the direction of the magnetic field it is in.
Why does a compass point North when not near a magnet?
Because the Earth generates its own magnetic field, which indicates that the Earth’s core must be magnetic.
What is a permanent magnet?
A magnet that produces its own magnetic field at all times.
What is an induced magnet?
A magnetic material that turns into a magnet only when it is placed inside a magnetic field.
What happens to an induced magnet when the permanent magnetic field is removed?
It quickly loses most or all of its magnetism.
What is the force between a permanent magnet and an induced magnet?
The force is always attractive.
What is created around a wire when an electric current flows through it?
A magnetic field made of concentric circles.
According to the Right-Hand Thumb Rule, what does the thumb and the curve of the fingers represent?
The thumb points in the direction of the current; the fingers show the direction of the magnetic field.
What two factors increase the strength of the magnetic field around a straight wire?
- Larger current.
- Being closer to the wire.
What is a solenoid?
A coil of wire that increases magnetic field strength because the field lines around each loop line up with each other.
Describe the magnetic field inside a solenoid.
It is strong and uniform (it has the same strength and direction at every point).
How can you further increase the strength of a solenoid?
By placing an iron core in the center (creating an electromagnet).
What is the Motor Effect?
When a current-carrying wire is placed in a magnetic field, the two fields interact, causing the wire and the magnet to exert a force on each other.
At what angle must a wire be to the magnetic field lines to experience the full force?
90 degrees (perpendicular). If it runs parallel, it feels no force at all.
Which rule is used to find the direction of the force in the motor effect?
Fleming’s Left-Hand Rule (Thumb = Force, First finger = Field, Second finger = Current).
Write the formula used to calculate the force on a conductor at right angles to a magnetic field.
Force = Magnetic flux density x current x length
What is Magnetic Flux Density and what is its unit?
It is the measure of how many field lines are in a region (the strength of the field). It is measured in Tesla (T).
A 0.5m wire carries 2A of current at right angles to a 0.1T field. Calculate the force.
0.1 x 2 x 0.5 = 0.1N
