Electric and Magnetic Fields

Question 0

Define electric field strength.

Answer 0

Force per unit positive charge

E = F/Q

Question 1

What unit is used for electric field strength?

Answer 1

N C^-1

Question 2

Potential gradient =

Answer 2

Electric field strength

V/d

Question 3

What creates electric fields?

Answer 3

Electric charges

Question 4

Unit for magnetic flux

Answer 4

Weber - Wb

Question 5

Unit for magnetic flux density

Answer 5

Tesla

Question 6

Faraday’s Law of electromagnetic induction

Answer 6

The magnitude of induced e.m.f. is equal to the rate at which the magnetic flux is cut

Question 7

Lenz’s Law

Answer 7

The direction of any induced current is in a direction that opposes the flux change that causes it

Question 8

A.C. Generator

Answer 8

A generator that, via the use of slip rings, produces an alternating e.m.f. and so an alternating current

Question 9

Alternating current

Answer 9

Electric current that reverses its direction with a constant frequency.

Question 10

Ammeter

Answer 10

A device used to measure electric current, connected in series with the components

Question 11

Conductor

Answer 11

A material with a high number density of conduction electrons and therefore a low resistance

Question 12

Conventional current

Answer 12

A model used to describe the movement of charge in a circuit.

Conventional current travels from + to -

Question 13

Coulomb’s law

Answer 13

The force between to charges is proportional to the product of the charges and inversely proportional to the square of the distance between the charges

Question 14

Efficiency

Answer 14

The ratio of useful output energy to total input energy

Question 15

Electric charge (Q or q)

Answer 15

Current x Time

Measured in Coulombs (C). Scalar quantity

Question 16

Electric current

Answer 16

A flow of charge

Vector quantity, measured in amperes (A)

Question 17

Electric field strength (E)

Answer 17

Force per unit charge

Given by E=F/q

Measured in N C^-1

Question 18

Electric field

Answer 18

A region of space where a charged particle experiences a force

It goes from + to -

Question 19

Electromagnetic Induction

Answer 19

The process of inducing e.m.f. using a magnetic field and a changing flux linkage

Question 20

Electromagnetic wave

Answer 20

A self-propagating wave that does not require a medium to travel through

Question 21

E.m.f.

Answer 21

The electrical energy transferred per unit charge when one form of energy is converted into electrical energy

Measured in volts (V)

Question 22

Electron flow

Answer 22

The movement of electrons (usually around a circuit), from - to +

Question 23

Electronvolt

Answer 23

One electronvolt is the energy change of an electron when in moves through a potential difference of one volt

Question 24

Fleming's LEFT hand rule

Answer 24

Used with electric motors and forces acting on moving charges in magnetic fields It shows the direction of force on a conductor carrying a current in a magnetic field. Force - thumb, field - first finger, current - second finger, all at right angles to each other

Question 25

Fleming's RIGHT hand rule

Answer 25

Used with generators and electromagnetic induction It shows the direction of the induced current when a conductor moves through a magnetic field Force - thumb, field - first finger, current - second finger, all at right angels to each other

Question 26

Induced e.m.f.

Answer 26

The e.m.f. produced by electromagnetic induction

Question 27

Insulator

Answer 27

A material with a small number density of conduction electrons and therefore high resistance

Question 28

Lenz's law

Answer 28

When a magnet is moved in a coil of wire, the coil has an induced e.m.f. If connected in a circuit, the coil itself produces a magnetic field. This magnetic field opposes the magnet

Question 29

Define magnetic flux

Answer 29

The product of magnetic flux density and the area at right angles to the flux

Question 30

Define ampere

Answer 30

SI unit for electric current

Question 31

What is alternating current?

Answer 31

Electric current that reverses its direction with a constant frequency

Question 32

What is an a.c. generator?

Answer 32

A generator that, via the use of slip rings, produces an alternating emf and so an alternating current

Question 33

Define magnetic flux density

Answer 33

The strength of the magnetic field

Question 34

Define magnetic flux

Answer 34

The product of magnetic flux density normal to a circuit and the cross-sectional area of the circuit.

Question 35

Define magnetic flux linkage

Answer 35

The product of the magnetic flux and the number of turns

Question 36

Define intensity

Answer 36

Power per unit cross-sectional area

Question 37

Define what is meant by a uniform electric field

Answer 37

A region between two objects of different electric potential in which a charged particle will feel a force and the strength of the force is the same at any point in the field. Field lines are equispaced.

Question 38

What is a magnetic field?

Answer 38

Region where a force is exerted on magnetic material Field lines go from north south (direction a north pole would feel a force in the field).

Question 39

What is the law of conservation of charge?

Answer 39

Electric charge cannot be created or destroyed | Positive and negative charges can make each other neutral