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Additional Physics Edexcel
Atoms have a positively charged nucleus and negatively charges electrons around it. This gives the atom an
overall neutral charge as there is the exact same number of protons and electrons.
Objects can be either positively or negatively charged or neutral.
When an object gains electrons it becomes negatively charged and when it loses electrons it becomes
Like charges repel and opposite charges attract.
Static electricity is caused by friction:
Two insulating materials are rubbed together causing electrons to be scraped off one and dumped on the
other. This will leave a positive charge on one and a negative charge in the other.
Only electrons can move and not protons is because the protons are fixed in the middle.
The way in which electrons are transferred depends on the materials involved.
There are 2 examples:
1. Polythene rod being rubbed with a cloth duster
Electrons move from the duster to the rod therefore the rod becomes
negatively charged and the duster positively charged.
2. Acetate rod being rubbed with a cloth duster
Electrons move from the rod to the duster therefore the duster becomes
negatively charged and the rod positively charged.
Static electricity can cause electric shocks.
You can get an electric shock if you are charged and touch something that is earthed(doesn't have a charge)
or you touch something that is charged.
1. For example as you walk on a nylon carpet, electrons are transferred from the carpet to you and charge
will build up due to friction. When you touch a metal door handle the charge will flow causing an
electrostatic shock because you just earthed yourself.
2. You can also get car shocks because a static charge builds up between clothing and synthetic car seats-
friction causes electrons to be scraped off and when you touch the metal door a charge flows.
3. Clothing crackles causes little sparks because electrons are scraped off leaving static charges. This leads
to the attraction and sparks as the charges rearrange themselves.
4. Balloons can stick to walls by rubbing the balloon against a jumper, this causes electron to be
transferred to the balloon leaving a negative charge. Even though the wall is not charged, the balloon
sticks because can move a little, so the negative charges on the wall repel the negative charge of the
balloon leaving the positive charges on the surface which attracts the negatively charged ballo0n. This
attraction holds the balloon on the wall.
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A charged comb can pick up small pieces of paper as electrons are transferred to the comb as it goes
through the hair leaving a negative charge on the comb. The reason why it picks up paper even though they
have no charge is because of induction in the paper which means they stick to the comb.
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Charge and current
An electrical current is the rate of flow of charge.
The charge is carried by electrons and they are able to move around therefore making metals good
In a circuit, in order for an electrical current to flow it needs:
1. A complete circuit