P4.1 - Wlectrical Charges And Fields (Finished) Flashcards
An uncharged atom has an equal number of ___
Electrons and protons
What can be transferred to or from an atom causing +ive and -ive charges?
Only electrons
What makes an atom negatively or positively charged?
Adding electrons to an uncharged atom makes it negatively charged, removing them makes it positively. As electrons have a -ive charge
How does friction cause static electricity?
When insulating materials are rubbed together negative electrons will be scraped off one and put on the other. This will leave the materials electrically charged with a positive charge on one and equal negative charge on the other.
What is the classic example of static electricity caused by friction?
Polythene rod and cloth
Why does too much static electricity cause a spark?
As electric charge builds up on an object the potential difference between it and the earth increases. If it is large enough electrons can jump across the gap between object and earth which is a spark.
When two ___ objects are brought close together they ___ on eachother
Electrically charged, exert a force
What is electrostatic attraction/repulsion?
The force exerted by two electrically charged objects on each other
Like charges ___, unlike charges ___
Repel, attract
How do you show electric fields on paper?
You use field lines to show electric fields around an object.
What are the rules for drawing electric field lines?
The electric field lines go from +ive to -ive , They are always at a right angle to the surface, the closer the lines, the stronger the field
What is an electric field created by?
An electric field is created around an electrically charged object
Why do charged objects in an electric field feel a force?
The electric fields of each charged object interact with each other causing a force to act on the objects
What varies the strength of an electric field?
- The charge of the object
- The distance from the object
Why does varying p.d. Cause sparks? (Electric fields)
A high potential difference causes a string electric field between charged object and earthed object. This field causes electrons in the air particles to be removed (ionised). Air is normally an insulator but when it is conductive a current can flow through it (a spark)
