Physics 4 -Electricity

Question 1

Charge is carried by what in solids

Answer 1

electrons (negatively charged)

Question 2

Charge is carried by what in liquids

Answer 2

Charged Ions

Question 3

Delocalized electrons are found where?

Why are they good conductors

Answer 3

Metals

Allows electrons to move around

Question 4

In thermal conductors, what is passed from one particle to particle

Answer 4

kinetic energy

Question 5

With a polythene rod, which way does electrons move to with the duster

What happens to the charge of the duster?

Answer 5

Duster –> Polythene rod

Duster becomes positive charged

Question 6

With the acetate rod, which way does electrons move?

What happens to the charge of the duster?

Answer 6

Acetate –> Duster

Duster becomes negatively charged

Question 7

Opposite charges…?

Answer 7

attract

Question 8

static electricity is created when

Answer 8

Two insulating materials are rubbed together

Of the insulators gets a load of electrons dumped on it
Like charges try and repel and cant as they are stuck

Creating static charge

Question 9

What creates a spark with static charge

Answer 9

Electrons realigning themselves

Question 10

what type of clothing is notorious for building up static charge when rubbed against eachother

Answer 10

Synthetic clothing

Question 11

What can solve static electricity problems

Answer 11

Earthing

Question 12

What is used to earth

What does this allow

Answer 12

Conductor (copper wire)

easy route for static charge to go to the ground

Question 13

Current is what

What units

Answer 13

flow of electric charge around the circuit

Amperes (amps)

Question 14

Voltage is what

Answer 14

Is whats needed to cause current to flow through a component

Question 15

the greater the resistance across a component, the smaller the ……..

Answer 15

current that flows through

Question 16

Current =

Answer 16

Time

Question 17

Charge is measured in

Answer 17

Coulombs

Question 18

Potential Difference is the ….

Answer 18

Work done per unit charge

Question 19

PD (V) =

Answer 19

  Charge (Q)

Question 20

What does a voltmeter measure

Answer 20

Potential Difference between two points

Question 21

On the circuit diagram, which way does the current flow from (on the battery)

Answer 21

Comes out of the thin lined one

Question 22

Current through a resistor is directly proportional to what

Answer 22

P.D. (voltage)

Question 23

In a filament lamp, as temperature increases, what happens to resnstance

Answer 23

Increases

Question 24

resistance from heat increases with temperature why

Answer 24

Ions in conductor vibrate more

Meaning electrons cant move through easily

And current cant flow easily

Question 25

V =

Answer 25

I x R

Question 26

Energy transferred(power) =

Answer 26

Power x Time

Question 27

Power=

Answer 27

Current x Potential Difference

Question 28

Energy transferred (charge) =

Answer 28

Charge x Potential Difference

Question 29

electromagnetic Induction

Answer 29

Creation of a potential difference across a conductor which is experiencing a change in magnetic field

Question 30

What 4 factors affect the size of the induced voltage from an elecromagnetic induction

Answer 30

Strength of magnetic field Cross sectional area of the coil Number of turns on coil Speed of movement

Question 31

If your turning the magnet faster, what two things will happen?

Answer 31

Higher peak voltage Higher frequency

Question 32

using flemings right hand rule, what does each finger show

Answer 32

thumb - Motion (direction of coil) 1st finger - Field (north-south) 2nd finger - current (points towards -)

Question 33

Transformers only work on what

Answer 33

A.C current

Question 34

Step up transformers have a higher P.D across which coil?

Answer 34

secondary coil

Question 35

Step down transformers have a higher P.D across which coil?

Answer 35

Primary coil

Question 36

Transformer equation with current

Answer 36

V(p) I(p) = V(s) I(s)

Question 37

Transformer equation with turns

Answer 37

V(p)/V(s) = N(p) / (Ns)

Question 38

Switch Mode Transformers operate between?

Answer 38

50KHz - 200KHz

Question 39

Switch mode operate at a higher?

Answer 39

frequency to traditional transformers

Question 40

Mains supply frequency is ?

Answer 40

50Hz

Question 41

What do Isolating transformers do?

Answer 41

the dont connect to the mains hence are safer

Question 42

how many turns are on the primary/secondary coils in an isolating system?

Answer 42

Equal number

Question 43

Is the voltage changed in an isolating transformer?

Answer 43

no

Question 44

Power loss =

Answer 44

Current^2 x Resistance

Question 45

If the current is 10x bigger, what happens to power loss?

Answer 45

100x larger