Year 10 term 2

Question 1

Defien current

Answer 1

rate of flow of charge

amount of charge passing through a component each second

Question 2

How does electricity get into your house?

Answer 2

From a main power source through a cable that is connected to a fuse box in your house.

Question 3

What does the fuse box contain

Answer 3

switches and breakers(to turn of the circuit if too much voltage/current) as well as the ring main

Question 4

What is in the ring main circuit?

Answer 4

3 main wires;
- neutral: completes the circuit
- Live wire: sends current around house
- Eart wire: incase something goes wrong, to re-direct charge so you are not hurt.

Question 5

How do the pins in a plug prevent electric shocks and keep you safe

Answer 5

They have a 3rd longer pin with the earth wire which enters the socket first, so electricity flows through it first rather than you.

Question 6

How does the fuse in the plug keep electronic safe?

Answer 6

The fuse has a metal wire and it completes the circuit- at hot temperatures the fuse wire melts so we say the fuse “blew”. This leads to incomplete circuit and stopping the flow of current.

Question 7

Where should a switch be placed-on the live or neutral wire? explain.

Answer 7

Live- if placed on the neutral current can still flow through the component visible through live wire and can lead to electric shock.

Question 8

Describe double insulation in circuits

Answer 8

The visible component has a plastic coating hence no need for a 3rd earth wire in ring main circuit, example:kettle.

Question 9

Volatage that household applaiances can have

Answer 9

220-240 V

Higher than mobile devices-hence dangerous

Question 10

Name 3 common fuse types

Answer 10

3A, 5A, and 13A

Question 11

What 2 factors effect current?

Answer 11

• How many electrons pass at a point(as different metals have different amounts of delocalized electrons)
• How fast these electrons are moving(to pass through this point)

Question 12

What is convectional current?

Answer 12

• A theoretical, false.
• “current” moving from positive to negative terminal

Question 13

1 Amp is equal to (-) Coulombs?

Answer 13

1C

*1 Amp=1 Coulomb

Question 14

How do the electrons in a circuit turn on the bulb?

Answer 14

By giving it their energy; They have kinetic energy as they move through thte circuit

*ELECTRONS CANNOT GIVE THEIR CHARGE.

Question 15

Equation linking charge, current and time

Answer 15

I=Q/t

Question 16

The size of the electric current is dependent on….

Answer 16

the rate of the flow of charge

Question 17

How do i measure current?

Answer 17

With an ammeter

Question 18

Define power

Answer 18

amount of energy transferred per second

Question 19

equation for power

Answer 19

P=IV

Question 20

Defien Voltage

Answer 20

Amount of energy transferred per unit of charge per second

the push given to electrons

Question 21

Equation of voltage

(the push given)

Answer 21

V= E/Q

amount of energy given(push given)/electron

Question 22

Voltage in series

Answer 22

SHared amongst components

Question 23

Voltage in parallel

Answer 23

Same throughout

hence bulbs have the same brightness

Question 24

Resistance depends on

Answer 24

• temperature
• Cross section length of wire
• length of wire

Question 25

In parallel, energy is ----- at a junction

Answer 25

conserved

Question 26

More power in an appliance means.....

Answer 26

- More work can be done in the same amt. of time - Same work can be done in less time

Question 27

What is the question hinting you to do if it says "ignore air resistance"?

Answer 27

use total energy equivelancy

Question 28

GPE basically means

Answer 28

The energy required to overcome the gravitational field

Question 29

Why does energy get transferred to a thermal store when current flows through a resitor?

Answer 29

As electrons flow they are in motion and therefore have KE, however thye do not flow in straoght lines and typically collide with e/o hence their KE store(some of it) is typically transferred to thermal energy which is dissipated to surroundings hence the temperature increses.

Question 30

shape of an IV graph in diode

Answer 30

weird shape-althoguh not clear which direction. WHen current flows through one direction and diode does not allow it to pass, there is no current so V/I when calculated gives you a high resistance, and vice versa when it flows through the other directionf romt he mains it allows current so V/I gives low resistance.

Question 31

IV graph of filament bulb

Answer 31

Steep slope at first but begins to curve- as voltage increases current increases so resistance then increase. When this increases the temperature current(and voltage) cannot stay constant. So graph curves more.

Question 32

General rule of IV graphs for resistance in terms of the slope

Answer 32

The steeper the slope the smaller the resistance. If it's a straight line that means resistance is constant.

Question 33

Defien alternating current with an example

Answer 33

IN a mains power supply, the current supplied increases and decreases, then this pattern repeats(same for voltage) in the opposite direction. When graphed it makes a wave, this is alternating current(/voltage) as current flows through one direction then the opposite.

Question 34

Defien direct current and an example.

Answer 34

Current only flows in one direction, and example is a cell or battery power supply, current is only one direction because voltage supplied is also only one direction.

Question 35

where are thermistors found?

Answer 35

temperature senors: - ovens - refrigerrators - fire alarms - boilers - washing machines

Question 39

LDR in

Answer 39

street lights

Question 40

LDR graph and thermistor graph

Answer 40

inversely proportional to resistance

Question 41

LEDS are a type of

Answer 41

diode

Question 42

Conductors

Answer 42

allow charge to pass hrough them easily. Have a delocalized electron

Question 43

SOme insulators can conduct, explain

Answer 43

In the form of static electricity if another insulator is rubbed on top, charge builds up and is then "conducted away"

Question 44

HOw to carry out investigation for static electricity(charging 2 insulators with friction)

Answer 44

1. Take a polsthene rod, rub both ends w/ a cloth, hang from nylon thread to cradle 2. take another material rod(e.g acetate) and rub cloth on ends 3. hang middle of other rod 4. hold rods close to each other 5. record observations ## Footnote *make sure you use different cloths

Question 45

charge of a polythene rod once rubbed wuth a cloht

Answer 45

negative as gains electrons

Question 46

CHarge of perspex or acetate rod once rubbed

Answer 46

positive as looses electrons

Question 47

how to improve static electricity practical

Answer 47

- also record pieces of paper picked up - graph results and conclusion created ## Footnote FRICTION

Question 48

How does static charge in us build up?

Answer 48

- rubbing on carpet - fibres in clothes(insulators) let built up negative charge stay on us until they have neutral surface to escape to(conductors)

Question 49

Static electricity in photocopier

Answer 49

- postively charged plate - light shines on plate to remove/neutralizze charge on other areas of plate - negatively charged toner particles atracted to positive plate - paper laid on to toner and toner is heated - image transferred

Question 50

Static charge in insecticide spray

Answer 50

- spray must cover alot of ground - particles given static charge i.e one charge (eg positive) - particles repel and if positively charged are attracted to negative earth particles hence alot of area covered ## Footnote similar technique for cars

Question 51

hazards of statis electricity sparks

Answer 51

- thunder/electrocution - sparking flammable gas

Question 52

preventing hazards of sparking in static electricity

Answer 52

- earthing plates at gas stations to avoid build up of negative charge - earthing copper wire in aeroplane for pipe and feul friction

Question 53

ratio of split of current at junction

Answer 53

determined by resistance of branch

Question 54

Why is current conserved at junction?

Answer 54

current enetering must = current leaving ## Footnote ratio depends on resistance of each branch

Question 55

power is the...

Answer 55

rate of energy transferred ## Footnote hence P=IV

Question 56

rearranging P formula to find max of something

Answer 56

Max=Max/min

Question 57

hazards of circuits

Answer 57

- damged insulation - overheating - damp conditions; water= conductor

Question 58

prevent hazards

Answer 58

- double insulation - breakers with electromagnets to break circuit in certain area(in fuse box) - fuse - earth wire to protect us

Question 59

earthing

Answer 59

each wire has diff amt of current, wire connected to earth to protect

Question 60

current/PD through each wire

Answer 60

- live wire: most with 230V - Neutral: 0V but can still shock - Earth wire: carries to earth if live wire touches casing

Question 61

why should electriction switch off main?

Answer 61

- electricity still flows through live wire if appliance off - difference of 230V - can shock

Question 62

DC has...

Answer 62

fixed positive and negative terminals, obtained frm circuit w/ battery

Question 63

DC graph

Answer 63

straight line, current one direction, constant V

Question 64

Ac from... Ac has...

Answer 64

- Generator, switches between 2 terminals - no fixed direction so current is postive or negative depending on direction(as power supply has 2 terminals, so current flows 2 ways)