electricity and magnetism Flashcards

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1
Q

permenant magnet

A

steel

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2
Q

magnetic material

A

iron

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3
Q

how to induce magnetism

A

a nail is made into a permenant magnet by its closeness to a permenant magnet

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4
Q

demagnetisation of magnet simple

A

heat it or hit it with a hammer

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5
Q

what is a magnetic field

A

a region where a magnetic pole experiences a force

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6
Q

what is the only test for a magnet

A

repulsion

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7
Q

how to make a permenant magnet ( complex)

A

place steel rod inside coil, use high dc current, leave steel inside, turn of current

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8
Q

how to change the strength of an electromagnet

A

increase current
use iron core
more turn in wire

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9
Q

examples of electromagnets

A

electric bells
loudspeakers

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10
Q

charging negative rod by friction

A

both cloth and rod contain equal number of protons and electrons
rub plastic polythene ( white) rod with cloth, electrons move from cloth to rod
rod becomes negative

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11
Q

charging a positive rod by friction

A

both contain equal number of protons and electrons
rub acetate clear plastic rod move from rod to cloth
non-metals can be charged by friction

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12
Q

electric field

A

region where electric charge experiences a force
the greater the number of lines per unit area, the greater the strength of the electric field

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13
Q

electric fields directions diagram

A

+ = arrows away
- = arrows towards
+ - = charge goes from positive to negative
2 plates= from positive to negative

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14
Q

current formula

A

charge/ time

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15
Q

examples of conducters

A
  • metals, because they have free electrons
  • carbons is a conducter
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16
Q

insulators

A
  • no free elecrons
  • water
17
Q

relationship between current and temperature

A

when temperature increase the flow of current decreases and resistance increases

18
Q

what is p.d

A

pushes electrons, gives them energy to move around a circuit
work by unit charge passing through a component

19
Q

p.d formula

A

p.d= work/charge

20
Q

cells in series

A

the total pd adds up

21
Q

what is resistance

A

the opposition to the flow of current

22
Q

resistance formula

A

resistance- p.d/current

23
Q

conventional current

A

opposite to flow of electrons

24
Q

what is emf

A

the work don per unit charge by the cell converting chemical energy into electrical energy

25
Q

emf formula

A

E= W/Q

26
Q

what do electrical circuits do

A

transfer energy from a sourse of electrical energy like cells, to the circuit component and then to the surroundings as heat energy

27
Q

power

A

the rate of doing work ( changing energy)

28
Q

power formula

A

energy change/ time
p.d x current

29
Q

ohms law

A

current is porportional to potential diference
VIR

30
Q

series circuit current, resitance and p.d

A

p.d adds, V= V1 + V2
current is the same everywhere
R= R1 + R2

31
Q

parrallel circuits p.d, resitance, and current

A

current adds up, I1 + I2
p.d is the same everywhere
R=R1 x R2/R1 + R2

32
Q

advantages of parallel circuits

A

all components can be awitches on and off independently
if a lamp breaks it does not affect the others
components recieve the pd it was desighned for

33
Q

the total resistance of a parallel circuit is…

A

less that any resistor in that circuit

34
Q

potential divider

A

can be 2 resistors in resirors in series or variable resistor with 3 connections. used for dimmer

35
Q

potential divider formula

A

Vout=R1/R1 +R2 x Vin

36
Q
A