Topic 6 - electricity ( year ten )

Question 1

What is the national grid ?

Answer 1

• The national gird consists of a system of transformers and high-voltage cables .
• (although the national grid connects powerstations to -homes , ONLY the transformers and cables are actually called the national grid ).

Question 2

What is the problem with gettign electricity to homes ?

Answer 2

-Energy is always lost in power cables due to resistance of the ires . (Bigger the disrance between powerstation and homes , a greater amount of energy is lost ).

Question 3

How do we fix the porblem of energy loss ?

Answer 3

We can reduce enrgy loss by buildiig power stations near hmes . But people don’t really want t live near powerstations .
-Another way to solve this problem is to use transformers .

Question 4

How does a transformer work ? stage one .

Answer 4

• Eleectricity passes through step up transformers which increase the potential difference to several hundred thousand volts .
• This is because less enegry is lost int he powercables when the potential diference is bery high .

Question 5

How does a transformer work ? stage wo .

Answer 5

-So the neergy passes through high-volage cables , but this can’t be passes onto homes , as potential difference would be too high .

Question 6

How does a transformer work ? stage three .

Answer 6

So finally , electricity passes through step-down transformers and they reduce the potential difference to around 230 V and then is passed into homes .

Question 7

What are good conductors of eelciticity , why ?

Answer 7

Metals are as electrons can flow through mttals .

Question 8

What are insulators of electricity adnd why ?

Answer 8

Plastic and glass are examples of insualtors as hey cannot conduct electricity as elecrons cannot move through insulators .

Question 9

Plastic rod rubbing agaisnt cloth (1)

Answer 9

• Cloth is an insultor (it is coevered with ellectrons , these cannot move through cloth as cloth is an insultor )
• Plastic is also an insulator (covered with electrons etc ).

Question 10

Plastic rod rubbing agaisnt cloth (2)

Answer 10

-If we were to rub the plastic rod against the cloth , electrons from the plastic rod move to the cloth .

Question 11

Plastic rod rubbing agaisnt cloth (3)

Answer 11

-As electrons have moved onto the cloth , the cloth now hasan overall negative charge .
-The plastic rod has lost electrons , so now has an equal positive charge (same size as the cloth charge )
scientists call this STATIC ELECTRICITY .

Question 12

What happens in a Van De Graaff generator (1) ?

Answer 12

(Top dome removed)

-As the belt moves , eleecrons pass from the top plastic roller onto the belt .

Question 13

What happens in a Van De Graaff generator (2) ?

Answer 13

-As the belt moves across the bottom plasic roller , elecrons pass off the belt and are transferred to Earch .

Question 14

What happens in a Van De Graaff generator (3) ?

Answer 14

-Meaning overtime , the top region of the generator becomes positively charged .

Question 15

What happens in a Van De Graaff generator (4) ?

Answer 15

-The dome on the generator acts as a store of positive charge - positive chage now builds up on the metal dome , allowign it to spread out .

Question 16

What happens in a Van De Graaff generator (5) ?

Answer 16

Person holding onto the generator ,has an overall positive charge ,a s the hairs on the head are positive , they repel eachother and move apart .

Question 17

Sparks

Answer 17

Electrostatic charge can build up as the fuel flows through refuelling pipe This could cause a spark and trigger an explosion . (Aircraft refueling) .

Question 18

How to prevent sparking ?

Answer 18

To prevent this , both refuelling truck and aeroplane are earthed , this prevents any charges from building up and leading to a spark .

Question 19

What is Static Electricity

Answer 19

• When two insulators are rubbed together electrons can pass from one to another .
• When an insulator GAINS electrons , it becomes negtivel charged and when it loses electrons , it becoes positively charged .

Question 20

-electric field shwon using fieldlines .
Filedlines must be PERPENDICULAR to the surface of the obkect (at 90 degrees ) !!!
-arros onn field line show direction of force .

Answer 20

field lines for a positie object go out
and field lines for a negaitve object go in .
-s you increase hte distnce betwene objects , the force gets bigger s it is clsoe to the center of positive /negative charge .
*further away , furter to the center of posiive/negative charge .