electricity and magnetism

Question 1

permenant magnet

Answer 1

steel

Question 2

magnetic material

Answer 2

iron

Question 3

how to induce magnetism

Answer 3

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

Question 4

demagnetisation of magnet simple

Answer 4

heat it or hit it with a hammer

Question 5

what is a magnetic field

Answer 5

a region where a magnetic pole experiences a force

Question 6

what is the only test for a magnet

Answer 6

repulsion

Question 7

how to make a permenant magnet ( complex)

Answer 7

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

Question 8

how to change the strength of an electromagnet

Answer 8

increase current
use iron core
more turn in wire

Question 9

examples of electromagnets

Answer 9

electric bells
loudspeakers

Question 10

charging negative rod by friction

Answer 10

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

Question 11

charging a positive rod by friction

Answer 11

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

Question 12

electric field

Answer 12

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

Question 13

electric fields directions diagram

Answer 13

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

Question 14

current formula

Answer 14

charge/ time

Question 15

examples of conducters

Answer 15

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

Question 16

insulators

Answer 16

• no free elecrons
• water

Question 17

relationship between current and temperature

Answer 17

when temperature increase the flow of current decreases and resistance increases

Question 18

what is p.d

Answer 18

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

Question 19

p.d formula

Answer 19

p.d= work/charge

Question 20

cells in series

Answer 20

the total pd adds up

Question 21

what is resistance

Answer 21

the opposition to the flow of current

Question 22

resistance formula

Answer 22

resistance- p.d/current

Question 23

conventional current

Answer 23

opposite to flow of electrons

Question 24

what is emf

Answer 24

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

Question 25

emf formula

Answer 25

E= W/Q

Question 26

what do electrical circuits do

Answer 26

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

Question 27

power

Answer 27

the rate of doing work ( changing energy)

Question 28

power formula

Answer 28

energy change/ time p.d x current

Question 29

ohms law

Answer 29

current is porportional to potential diference VIR

Question 30

series circuit current, resitance and p.d

Answer 30

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

Question 31

parrallel circuits p.d, resitance, and current

Answer 31

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

Question 32

advantages of parallel circuits

Answer 32

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

Question 33

the total resistance of a parallel circuit is...

Answer 33

less that any resistor in that circuit

Question 34

potential divider

Answer 34

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

Question 35

potential divider formula

Answer 35

Vout=R1/R1 +R2 x Vin