5.6.1 Electromagnetic Effects (up to transformers)

Magnetic Effect of a Current
> M__ charges = magnetic field

USE __ HAND GRIP RULE:
thumb = c__ direction
fingers = magnetic field d__

moving, right, current, direction

Solenoid
> c__ of c__ carrying wire that produces a m__ field

coil, current, magnetic

Motor Effect (Force on a Current-Carrying Conductor)
> via F__’s __ hand rule
thumb = m__
first finger = f__
second finger = c__

flemings, left, movement, field, current

current is going __ of the page

out

current is going __ the page

into

Motor effect (Left hand)
↑force on wire when:
Ø  ↑c__
Ø  ↑# of w__
Ø  ↑m__ field str.
Ø ↑l__ of wire

current, wires, magnetic, length

Current flow for the +ve charge is going __

right

Current flow for the -ve charge is going __

left

Relays
> electronic s__ operated by a m__ coil
o   ↑p.d. = magnetic field of relay closes switch = O__
o   ↓p.d. = switch remains open = O__

switch, magnetising, ON, OFF

D.C. motor
>  C__-carrying wire in a m__ field experiences a t__ effect
>   To ↑turning effect:
>> # of t__ on coil
>> incr c__
>> incr str. of m__ field

current, magnetic, turning, turns, current, magnetic

DC MOTOR: Split ring communicator
>  R__ c__ direction every __ turn to keep coil r__ in the same direction
>  No split ring c. = coil flips f__ & backwards

reverses current, 1/2, rotating, forwards

DC MOTOR: Carbon brushes
> ensures c__ is m__ without t__ wires

current, maintained, tangling

Why does a DC motor need a split ring communicator

to reverse current

Why does an AC generator NOT need a split ring communicator

current is alr changing

Energy conversion
Motor effect	E__ → m__ (kinetic)
EM induction	M__ (kinetic) → e__

electric, mechanic, mechanic, electric

AC generators convert m__ → e__ energy

motion, electrical

AC generator
Magnet: provides const. m__ field
Coil: c__ magnetic field as it r__ & allows i__ current to flow
Slip rings: allow d__ of induced e.m.f. to alt. = a.c.
Carbon brushes: electronic connection between coil & circuit ;; prevent wires getting t__

magnetic, cuts, rotates, induced, direction, twisted

AC: At vertical, there is no c__ = _V

cutting, 0

AC: every half (start, middle, end), it will be v__

vertical

Operating AC generators
Ø  Rectangular c__ rotates in uniform m__ field
Ø  Coil is connected to external c__ via slip rings & brushes
o   Use g__ to measure induced e.m.f. in coil
Ø  e.m.f. is induced in the coil as it c__ the magnetic field
o   R__ proves e.m.f. is always c__
Ø  Alternating e.m.f. = a.c.

coil, magnetic, circuit, galvanometer, cuts, rotation, changing

Motion of an A.C. Generator
M__ e.m.f. induced when:
>  H__ pos. & coil motion is p__ to the field
>>   Bc most # of l__ cut when coil moves perp. to the field
No e.m.f. induced when:
>  V__ pos. & coil motion is p__ to the field
>> Bc no lines cut when coil moves parallel to the field

max, horizontal, perpendicular, lines, vertical, parallel

AC graphs
> if starting horizontally (max emf), it is a __ curve
> if starting vertically (0 emf), it is a __ curve

cosine, sine

Factors Affecting an A.C. Generator
↑induced e.m.f. magnitude by:
o   ↑freq. of r__ of the coil
o   ↑# of t__ on the coil
o   ↑str. of m__
o   Inserting soft i__ core into the coil

rotations, turns, magnet, iron

THUS, AC is made by:
Ø  Coil r__ in magnetic field
Ø  M__ rotating w__ a coil
Both induce e.m.f. as coil has changing m__ field

rotating, magnet, within, magnetic