electromagnets Flashcards
How to calculate the force on a wire carrying a current at right angles to a magnetic field
To calculate the force on a wire carrying a current at right angles to a magnetic field, use the equation:
force = magnetic flux density × current × length
This is when:
F is force in newtons (N)
B is magnetic flux density (magnetic field strength) in tesla (T)
I is current in amperes - also referred to as amps (A)
is length in metres (m)
The force on a given length of wire in a magnetic field increases when:
the current in the wire increases
the strength of the magnetic field increases
What are the main components in a loudspeaker?
A loudspeaker needs a coil of wire, permanent magnet and a cone
What is the split ring commutator part of
The split ring commutator is a part of a dc motor.
When using Fleming’s left hand rule, what does the thumb represent?
In Fleming’s left hand rule, the thumb shows the force direction. The first finger shows the magnetic field direction.
When a current flows in a wire, what does it create
When a current flows in a wire, it creates a circular magnetic field around the wire. This magnetic field can deflect the needle of a magnetic compass.
when is the strength of the magnetic field greater
When:
it is closer to the wire
if the current is increased
What is a solenoid
A solenoid consists of a wire coiled up into a spiral shape. When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet. The field inside a solenoid is strong and uniform. The small magnetic fields caused by the current in each coil add together to make a stronger overall magnetic field.
What is an electromagnet
A solenoid with an iron core is called an electromagnet. The iron core increases the solenoid’s magnetic field strength. A simple electromagnet is made by coiling wire around an iron nail.
what are electromagnets used in
Electromagnets are used in devices such as electric bells, and door locks that can be controlled remotely.
What does a wire carrying a current create
A wire carrying a current creates a magnetic field. This can interact with another magnetic field, causing a force that pushes the wire at right angles. This is called the motor effect.
Fleming’s left hand rule - Higher
The force on a given length of wire in a magnetic field increases when:
the current in the wire increases
the strength of the magnetic field increases
For any given combination of current and magnetic field strength, the force is greatest when the direction of the current is 90° to the direction of the magnetic field. There is no motor effect force if the current and magnetic field are parallel to each other.
The direction of a motor effect force can be found using Fleming’s left hand rule.
how to work out magnetic field with hand
Hold your thumb, forefinger and second finger at right angles to each other:
the forefinger is lined up with magnetic field lines pointing from north to south
the second finger is lined up with the current pointing from positive to negative
the thumb shows the direction of the motor effect force on the conductor carrying the current
A coil of wire carrying a current in a magnetic field experiences a force that tends to make it ________
rotate. This effect can be used to make an electric motor.
How do speakers work
The motor effect is used inside headphones, which contain small loudspeakers. In these devices, variations in an electric current cause variations in the magnetic field produced by an electromagnet. This causes a cone to move, which creates pressure variations in the air and forms sound waves.
