# Magnetic Fields Flashcards

How do we work out the direction the the magnetic field around a straight current-carrying conductor?

Using the right hand rule, where your thumb is the current and your fingers are the direction of the magnetic field.

Describe the magnetic field around a straight current-carrying conductor.

Concentric circles around the wire.

Describe the magnetic field around a solenoid.

As a bar magnet, out the positive end and into the negative end.

When do we use Fleming’s left hand rule?

When a current-carrying wire is placed at right angles to a magnetic field.

What do each of the fingers used in Fleming’s left hand rule represent?

Thumb - Force

First finger - Field

Second finger - Current

In the equation F=BIL, what is B, and what is it defined as?

B is magnetic flux density and is defined as the force on one meter of wire carrying a current of one amp at right angles to the magnetic field.

Name and define the unit for magnetic flux density.

Tesla is defined as webers (Wb) per unit area.

When do we use F=BIL and F=BILsin(x)?

To work out the size of the force on a current carrying wire.

What is the difference between F=BIL and F=BILsin(x)?

They are the essentially the same equation, but when the current is perpendicular to the magnetic field, sin(x) is emitted because the angle is 90 and therefore sin(x) equals one. The angle is measured as the angle between the direction of the magnetic field and the direction of the current.

When do we use F=BQv?

To find the force on a single charged particle travelling at right angles through a uniform magnetic field.

How do charged particles travel through a magnetic field?

In a circular path.

Why do charged particles travel through a magnetic field in a circular path?

The force from the magnetic field is always perpendicular to the particle, which satisfies the conditions for circular motion. The force causes centripetal acceleration.

How will charged particles move in an electric field?

The force acting on them will accelerate them in a straight line.

How will charged particles move in a magnetic field?

In a circular path, with particles of higher mass moving in a circular path with a larger radius.

In a mass spectrometer, how are ions identified?

Using a detector connected to a computer, the mass to charge ratio is calculate and then searched for in a database that will detect the ions. Only ions of a particular mass to charge ratio pass through the detector due to the path of the ion varying with mass and charge.