Topic 11 Flashcards
How do objects become charged ?
Objects become charged when they gain or lose electrons. Charge is measured in Coulombs (C).
Why do like charges repel ?
An object can be positively charged or negatively charged.
Like charges repel each other.
Two positive charges will repel each other.
Two negative charges will also repel each other.
Why unlike charges attract ?
Unlike charges attract each other.
A negative charge and a positive charge attract each other.
How do objects become charged ?
Electrons are negatively charged.
Sparks.
Rubbing objects
When an object loses or gains electrons what happens ?
Electrons are negatively charged.
An object that loses electrons becomes positively charged and an object that gains electrons becomes negatively charged
How are sparks produced ?
When there is a difference between the positive and negative charge of two objects, there is a potential difference between the two objects. This potential difference causes a rapid transfer of charge. Energy is stored in an electrostatic store and a spark is produced.
In clouds during a storm, charge builds up and creates lightning, which is an example of a spark.
How does rubbing objects create charge ?
Rubbing an object against another object can cause electrons to jump from one object to the other. This causes both objects to become charged.
A plastic rod (or a balloon) can be charged by rubbing it with a cloth (or hair).
The charged rod will attract a gentle stream of water falling from a tap.
The charged rod can move an empty aluminium drink can. The charge on the rod attracts or repels the electrons in the metal, moving the can
What do conductors allow ?
charge to flow to earth, so they would not maintain (keep) this charge.
What do we We call objects with no conducting path (link) to earth ?
isolated objects
How is static electricity used in a photocopier?
The areas to receive ink are positively charged and the ink is negatively charged, which ensures an even coat of ink in the right places
How is static electricity used is insecticides ?
Insecticide is given an electrostatic charge when it is released.
The insecticide is then attracted to the earth so moves away from the sprayer.
There is a repulsion between the droplets of insecticide which means the droplets don’t clump together.
This gives an even layer of insecticide on the ground.
How do sparks build up when fulling a car ?
When fuel is pumped through a hose into a car, it rubs against the hose.
This results in an electrostatic charge building up due to friction
How can imperfections in the fuel and gaps in the hose system cause sparks ?
There are imperfections in the fuel and gaps in the hose system so charged fuel can escape as vapour (gas).
When gas leaks, a tiny spark can ignite the vapour (set it on fire) which can have catastrophic, explosive consequences.
Why is earthing important at a petrol station ?
It is important to make sure the hose supplying the fuel to the car is Earthed.
This reduces the risk of sparking from happening.
How does static electricity arise ?
Static electricity arises when electrons transfer from one object to another.
