Magnetic Fields

Question 1

What direction do Magentic Field lines follow

Answer 1

North to South

Question 2

When is a Magnetic Field induced

Answer 2

When current passes through a wire

Question 3

What is Magnetix Flux Density

Answer 3

The force per unit charge and length of a magnetic field, it is a measure of the strength of the field

Question 4

What is the Definiton of a Tesla

Answer 4

One Tesla is defined as a force of 1 N on 1 metre of wire carrying 1 A of current perpendicular to a magnetic field

Question 5

What is the equation of the force of a wire when it is placed into a magnetic field

Answer 5

F = B x I x L x Sin (θ)

Force (N) = Magnetic Fluex Density (T) x Current (A) x Sin( the angle from the field)

Question 6

When is the force of a wire placed in a magnetic field at it’s strongest

Answer 6

When the field is perpendicular to the current

Question 7

How do you find the direction of a force excerted on a wire

Answer 7

Flemming’s Left Hand Rule

• F - Force
• B - Magnetic Flux Density
• I - Conventional Current (opposite direction to electron flow)

Question 8

Describe the Magnetic Field Lines of different Bar Magnets

Answer 8

Question 9

Why is a force exerted on a current-carrying wire

Answer 9

• A force acts on charged particles moving in a magnetic field
• Therefore because the wire contains moving electrons, which are negatively charged, a force is excerted on the wire

Question 10

What is the Equation of the Force excerted on a particle when it is moving in a Magentic Field

Answer 10

F = B x Q x V

Force (N) = Magnetic Flux Density(T) x Charge (C) x Velocity (m/s)

Question 11

Which direction is the force excerted on a particle when it is moving in a magnetic field

Answer 11

• The force exerted is always perpendicular to the motion of travel
• This causes the charged particles to follow a circular path when in the magnetic field
• Because the force induced by the magnetic field acts as a centripetal force

Question 12

How would you find the radius of a particle’s circular path when it is inside a magentic field

Answer 12

• Combine the formulas of Centripetal Force and Magnetic Force on a charged particle
• F = BQV (Magnetic Force)
• F = mv² / r (Centripetal Force)
• QVB = mv² / r
• r = MV / BQ

Question 13

What is an application of the circular deflection of charged particles in a magnetic field

Answer 13

• A cyclotron (a particle accelerator)
• Cyclotrons produce ion beams for radiotherapy, and radioactive tracers

Question 14

Describe how a Cyclotron works

Answer 14

• A cyclotron is formed of two semi-circular electrodes called “Dees”
• The “Dees” have a uniform magnetic field acting perpendicular to the plane of the electrodes, and a high frequency alternating voltage applied between the electrodes
• The charged particles move from the centre of one of the electrodes, and are deflected in a circular path by the magnetic field
• Once the particles reach the edge of the electrode they begin to move across the gap between the electrodes, where they are accelerated by the electric field, meaning the radius of their circular path will increase as they move through the second electrode
• When the particles reach the gap again, the alternating electric field changes direction allowing the particles to be accelerated again
• This process repeats several times until the required speed is reached by the particles and they exit the cyclotron

Question 15

What is Magnetic Flux

Answer 15

The magnetic field passing through a given area, when the field is perpendicular to the area

Question 16

What is the Magnetic flux linkage

Answer 16

The magnetic flux multiplied by the number of turns of a coil

Question 17

What is the Equation for the Magnetic Flux Linkage

Answer 17

Nϕ = B x A x N x Cos(θ)

Magetic Flux Linkage (Wb) = Magnetix Flux Density (T) x Area (M²) x Number of Turns x Cos (The angle from the normal)