Magnetic Fields Flashcards
How is a magnetic field similar to electric and gravitational fields?
It’s a region in which a force acts
What is a magnetic field?
A region in which a force acts on magnetic materials or magnetically susceptible materials
How do you represent magnetic fields?
Field lines (also called flux lines)
What is the direction of field lines for a magnetic field?
From the north to the south pole of a magnetic
The closer field lines are together, the…?
Stronger the field is
How is a magnetic field induced around a wire?
When current flows in a wire, it induces a magnetic field
Describe the field lines for a magnetic field induced around a wire?
They are concentric circles centred around the wire
What rule do you use to work out direction of magnetic field in a current-carrying wire?
Right-hand rule (by wrapping hand around with thumb pointing in direction of current, direction of curled fingers shows direction of magnetic field?)
What is the magnetic field of a solenoid similar to?
Magnetic field of a bar magnet
Describe the magnetic field formed when you place a wire between 2 external magnetic fields (e.g. 2 magnets)?
The field around the wire and the fields from the magnets are added together, resulting in a resultant field
For the magnetic field around a current-carrying wire, what does a solid dot show?
• = current flowing out of the page, towards the reader
For the magnetic field around a current-carrying wire, what does a solid dot show?
⊗ = current going into the page, away from the reader
For the magnetic field of a current-carrying wire between 2 magnets, which direction is the resultant force of the field?
Perpendicular to both current direction and magnetic field
What is the resultant force of magnetic field of a current-carrying wire between 2 magnets equal to if the current is parallel to the field lines?
Resultant force = 0N
For Fleming’s left-hand rule, what does the first finger denote?
First finger = direction of uniform magnetic Field
For Fleming’s left-hand rule, what does the second finger denote?
SeCond finger = direction of conventional Current
For Fleming’s left-hand rule, what does the thumb denote?
ThuMb = direction of force (so direction of Motion)
What happens to a wire when you pass an alternating current through a wire in a magnetic field?
The wire vibrates
Why does a wire vibrate if you pass an alternating current through it in a magnetic field?
Because force is perpendicular to direction of current, so if current is reversed, direction of force is also reversed. Constant reversal of force means that the force is constantly alternating too, so up and down motion of wire
What is the magnetic flux density defined as?
The force on 1 metre of wire carrying a current of 1A at right angles to the magnetic field
What is magnetic flux density proportional to?
The force on a current-carrying wire at right angle to a magnetic field
What are the units of magnetic flux density?
Tesla (T)
Is magnetic flux density a scalar or vector quantity?
Vector, because it has both direction and magnitude
What is 1 tesla equal to?
1 tesla = 1 newton per amp per metre