6.3

Question 1

Magnetic field

Answer 1

Region around a permanent magnet or moving charge in which another body with magnetic properties will feel a force

Question 2

Magnetic field lines

Answer 2

Show the shape of the field and the direction a plotting compass would point at that point

Question 3

Solenoid

Answer 3

Long coil of current carrying wire

Question 4

How do we determine the direction of the magnetic field around a current carrying wire?

Answer 4

Right hand rule 👎🏻

Question 5

Magnetic flux

Answer 5

Product of the flux density B and the area A at right angle to the flux
Measured in Wb
Amount of magnetic field passing through a surface

Question 6

Magnetic flux density

Answer 6

Strength of the magnetic field
Flux passing perpendicular through an area
Measured in T or Wb m^-2

Question 7

Weber

Answer 7

Magnetic flux when a magnetic field of magnetic flux density 1 T passes at right angle through an area of one square metre

Question 8

Fleming’s left hand rule

Answer 8

Shows the direction of the force on a conductor carrying a current in a magnetic field
Force/thumb, field/first finger, current/second finger
(Conventional current)

Question 9

What is the relationship between the force on a wire and the angle between it and the field

Answer 9

SinA, A=0 they are parallel, no cutting

Question 10

How does a charge act when moving in a constant magnetic field?

Answer 10

Force acting perpendicular to motion produces circular motion in the particle, no force acting in direction of motion means no increase in speed

Question 11

How can you change the radius of the circle a charge makes moving in a field?

Answer 11

Increasing speed or mass increases the radius, increasing charge or field strength decreases radius

Question 12

How do mass spectrometers work?

Answer 12

Ions are fired into uniform magnetic fields, the radius of the circular path the ion follows is directly proportional to its mass

Question 13

Electromagnetic induction

Answer 13

Process of inducing an emf in a conductor when there is a change in the magnetic flux linkage across the conductor

Question 14

Induced emf

Answer 14

Emf produced by the electromagnetic induction

Question 15

Magnetic flux linkage

Answer 15

The product of the magnetic flux through a coil and the number of turns on the coil
Units are weber turns

Question 16

Faraday’s Law

Answer 16

Magnitude of the induced emf is equal to the rate of change of flux linkage

Question 17

Lenz’s Law

Answer 17

The direction of any induced emf or induced current is in a direction that opposes the flux linkage that causes it

Question 18

Search coil

Answer 18

Small, flat coil used to determine the strength of a magnetic field

Question 19

Generator

Answer 19

Device used to generate electricity in which the work done to turn the coil within the magnetic field is transferred to electrical energy. The rotation of a coil within a magnetic field produces a constantly changing flux linkage and so a constantly changing emf

Question 20

Alternating current

Answer 20

Electrical current that reverses its direction with a constant frequency

Question 21

Transformer

Answer 21

Device that can either increase or decrease the size of ac voltage with little power loss

Question 22

Ratios of transformers

Answer 22

Ns / Np = Vs / Vp = Ip / Is

Question 23

How do transformers increase efficiency

Answer 23

Iron core centres, that are laminated or made up of lots of thin layers of iron glued together reduce the effects of eddy currents

Question 24

Why is an iron core used

Answer 24

It has a high magnetic permittivity and concentrates the magnetic field or flux

Question 25

Why are the coils in a transformer close together

Answer 25

The closer the two coils are, the greater effect a changing magnetic field in the primary coil has on the secondary coil