Magnetism and Electromagnetism

These flashcards cover key concepts related to magnetism and electromagnetism, including the behavior of current-carrying wires, the operation of electric motors, and the principles behind loudspeakers.

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 and the distance from the wire.

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?

A force is exerted between a magnetic field and a current-carrying conductor placed in that field.

What does the forefinger represent in Fleming’s left-hand rule?

The forefinger points in the direction of the magnetic field.

What does the second finger represent in Fleming’s left-hand rule?

The second finger points in the direction of current flow in the conductor.

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 and the strength of the magnetic field.

What happens to the force if the direction of current in a current-carrying wire is reversed?

The direction of the force is reversed.

What happens to the force if the strength of the current is increased in a current-carrying wire?

The strength of the force is increased.

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.

How does an electric motor work?

A coil of wire carrying a current is placed in a magnetic field, causing rotational effects due to forces on the sides of the coil.

How do loudspeakers make use of the motor effect?

They convert variations in current into pressure variations that produce audible sound.

Explain how a loudspeaker works.

A cone with a wire connected to an a.c. power supply is placed in a magnetic field; current creates a second magnetic field that causes the cone to vibrate.

How is the pitch of the sound from a loudspeaker changed?

By altering the frequency of the a.c. current, changing the frequency of vibration in the cone.

What is the relationship between the distance from the wire and the strength of the magnetic field?

As the distance from the wire increases, the strength of the magnetic field decreases.

What is a solenoid?

A coil of wire that produces a magnetic field when carrying current.

What increases the strength of an electromagnet?

Adding an iron core to the solenoid increases the magnetic field strength.

In the motor effect, what is exerted between a magnetic field and a current-carrying conductor?

A force is exerted.

What happens to a loudspeaker cone when current flows through the wire?

It creates a second magnetic field that interacts with the permanent magnetic field, causing vibration.

What is the purpose of the a.c. power supply in a loudspeaker?

To provide alternating current that varies, producing changes in sound frequency.

What does the direction of the force depend on in a magnetic field?

It depends on the direction of the current and the orientation of the magnetic field.

What does the interaction of the two magnetic fields in a loudspeaker result in?

It produces a force that causes the cone to vibrate, creating sound.

How is the force on a current-carrying conductor in a magnetic field affected by the strength of the magnetic field?

The greater the strength of the magnetic field, the greater the force on the conductor.

What practical application uses the motor effect to produce sound?

Loudspeakers use the motor effect to convert electrical energy into sound.

What is the role of a coil in an electric motor?

The coil carries current and creates a magnetic field that interacts with external magnetic fields to generate motion.

What happens to the magnetic field intensity near a straight conductor carrying current?

The intensity decreases with increasing distance from the conductor.

What is the effect of increasing the current on the magnetic field's strength around a wire?

The strength of the magnetic field increases with the increase of current.

What does each finger represent in Fleming's Left Hand Rule?

Forefinger: magnetic field direction, Second finger: current direction, Thumb: force direction.

What type of current flows in a loudspeaker to create sound?

Alternating current (a.c.).

What does reversing the current in a wire within a magnetic field do to the motion?

It reverses the direction of motion of the conductor.

What mechanical effect is produced by a coil placed in a magnetic field?

A rotational effect resulting from opposing forces acting on the coil sides.