Electromagnetism Flashcards
What is electromagnetism?
Electromagnetism is when an electric current moving through a conductor generates its own magnetic field.
How does the strength of the magnetic field change with distance from the wire?
The magnetic field is strongest closer to the wire.
How does the strength of the magnetic field change if the current is increased?
The strength of the magnetic field increases if the current is increased.
What does the right hand grip rule determine?
The right hand grip rule determines the direction of the magnetic field produced by a current-carrying wire.
How is the right hand grip rule used?
The thumb points along the direction of the current while the other fingers determine the direction of the magnetic field.
Can a wire generate a magnetic field?
Yes a wire can generate a magnetic field when electricity is passed through it.
What is a solenoid?
A solenoid is a wire twisted into a spiral shape to create a strong uniform magnetic field inside the coil.
What happens to the magnetic field outside a solenoid?
Outside the solenoid the small magnetic fields cancel out one another making the magnetic field much weaker.
What does the magnetic field of a solenoid resemble?
The magnetic field of a solenoid resembles a bar magnet.
How can we increase the magnetic field of a solenoid?
The magnetic field can be increased by increasing the number of turns on the coil or by placing an iron core inside the solenoid.
How can the magnetic field of a solenoid be turned off?
The magnetic field of a solenoid can be turned off by stopping the electric current.
What is the motor effect?
The motor effect is when a wire carrying current experiences a force when placed in a magnetic field causing it to move in a particular direction.
What happens when a current-carrying wire is placed in a magnetic field?
The wire experiences a force that causes it to move in a particular direction known as the motor effect.
How does the force on a wire in a magnetic field change?
The force increases if the current in the wire increases or if the strength of the magnetic field increases.
When is the force on the wire the greatest?
The force is greatest when the wire is placed at 90o (perpendicular) to the magnetic field.
When is there no motor effect?
There is no motor effect when the current is parallel to the magnetic field.
How can the direction of movement of a wire in a magnetic field be predicted?
The direction can be predicted using Fleming’s left hand rule. The first finger points in the direction of the magnetic field the second finger in the direction of the current and the thumb shows the direction the wire moves.
What does Fleming’s left hand rule help determine?
Fleming’s left hand rule helps determine the direction of movement of a wire in a magnetic field when current is passed through it.
What is an electric motor?
An electric motor (also called a DC motor) is made up of a coil of wire in between two permanent magnets. Direct current runs through the wire and experiences a force (the motor effect) exerted on it by the magnetic field. This force causes the coil of wire to turn.
How does a split-ring commutator work in a motor?
The split-ring commutator causes the current to switch direction after every half-turn of the coil ensuring that a turning effect is experienced for every half-turn which keeps the motor turning.
What factors can increase the speed of an electric motor?
The speed of the motor can be increased by increasing the current or increasing the strength of the magnetic field or increasing the number of turns on the coil.
What are some common appliances that use electric motors?
Electric motors are used in appliances such as fans or drills or washing machines or electric whisks.
How do loudspeakers work?
Loudspeakers rely on the motor effect to work - they consist of a coil of wire between two permanent magnets which is wrapped around the base of a cone. The coil of wire experiences a force causing the coil to move back and forth. Since the coil of wire is connected to the cone these movements cause the cone to vibrate. The vibrations push air molecules around the cone producing sound waves.
