Electricity - static electricity

Question 1

when do objects become charged

Answer 1

when they lose or gain electrons

Question 2

what happens if you rub one object on another

Answer 2

Rubbing an object against another object can cause electrons to jump from one object to the other. This causes both objects to become charged.

Question 3

Charged rod example

Answer 3

When a polythene rod is rubbed with a duster, the friction causes electrons to gain energy. Electrons gain enough energy to leave the atom and ‘rub off’ onto the polythene rod.

the polythene rod has gained electrons, giving it a negative charge
the duster has lost electrons, giving it a positive charge
If the rod is swapped for a different material such as acetate, electrons are rubbed off the acetate and onto the duster.

the acetate rod has lost electrons, giving it a positive charge, can then attract paper
the duster has gained electrons, giving it a negative charge,

Question 4

What are objects with no conducting path to earth called

Answer 4

isolated objects

Question 5

when does static electricity happen

Answer 5

when electrons transfer from one object to another

Question 6

what are electric fields

Answer 6

All charged objects have an electric field around them, which shows how they will interact with other charged particles.
If another electrically charged object enters an electric field, the charged object will feel a force acting on it.

Question 7

what way will the arrows go in a positively charged electric field

Answer 7

outwards

Question 8

what do electric fields depend on

Answer 8

charge and distance

• The closer an object is to the charged object, the stronger the electric field.
  The higher the charge of the object, the stronger the electric field.

Question 9

what way will the arrows go in a negatively charged electric field

Answer 9

inwards

Question 10

HOW are sparks created

Answer 10

• as electric charge builds up on an object, pd between the object and the earth increases
• if potential difference between the two gets large enough, electrons can jump across the gap between, causing a spark

Question 11

what happens to the force acting on a negative charge as it moves closer to a positively charged object

Answer 11

1. The forces between the charges increases as they get closer together
2. This is because the force is caused by the electric fields of the charges interacting
3. Electric field gets stronger the closer you get to a charged object, so when the two objects are closer together, the field is stronger and they feel a larger force

Question 12

how do sparks happen ( explain using electric fields )

Answer 12

• a high pd causes a strong electric field between the charged object and earthed object
• the strong electric field causes electrons in the air particles to be removed (ionisations)
• air is usually an insulator but when ionised, its more conductive, so current can flow through it, this is the spark

Question 13

why are metals good conductors

Answer 13

because electrons can flow easily through them

Question 14

how does a van de graph work

Answer 14

• in the generator there is a moving belt
• as the generator moves, electrons pass from the top plastic roller onto the belt
• electrons pass off the belt and are transferred to the earth
• over time the top region becomes positive
• positive charge builds up on the metal dome
• man now has an overall positive charge