# Electricity

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Electricity

## 6. STATIC ELECTRICITY

### 6.1. LAW OF ELECTROSTATICS

6.1.1. Static Electricity is defined as an electrical charge caused by an imbalance of electrons on the surface of a material. This imbalance of electrons produces an electric field that can be measured and that can influence other objects at a distance.

6.1.2. Static electricity happens when the amounts of positive and negative electric charges within a material are not perfectly equal.

6.1.2.1. Closer = Stronger

6.1.2.2. Further = Weaker

6.1.3. The law of electrostatic states that like charges repel and unlike charges attract.

6.1.3.1. Like Charges

6.1.3.1.1. Positive + Positive

6.1.3.1.2. Negative + Negative

6.1.3.2. Unlike Charges

6.1.3.2.1. Positive + Negative

### 6.2. CURRENT

6.2.1. Electrical charges include electrons, protons and ions.

6.2.1.1. Electrons are Negative

6.2.1.2. Protons are Positive

6.2.2. Electric current is the flow of charges from the positive end to a negative end

6.2.2.1. The SI unit for measuring electric charge is Coulomb (Cs^-1)

6.2.2.2. The Symbol for Coulomb is Q

### 6.3. ELECTROSTATICS

6.3.1. Charging

6.3.1.1. Induction

6.3.1.1.1. Electrostatic charging is only for conductors

6.3.1.1.2. The charged object does not touch the sphere

6.3.1.1.3. The resultant charge on the sphere is opposite to charge of the inducing object

6.3.1.1.4. A ground is needed to create charge on the sphere or there will be no flow of electrons

6.3.1.1.5. The charges rearrange themselves in absence of charged inducing object

6.3.1.1.6. The direction of flow of elections is either from or towards the ground depending on the charge of the inducing object

6.3.1.2. Rubbing

6.3.1.2.1. Rub a balloon on the woolen sweater. Rub a glass rod on the silk scarf

6.3.2. Uses of Electrostatics

6.3.2.1. Flue-ash removal

6.3.2.1.1. Flue ash is a mixture of dust and smoke produced by many factories and power stations

6.3.2.1.2. Charged metal plates in the chimney attract these particles and remove them from the exhaust gases

6.3.2.1.3. Charged metal plates in the chimney attract these particles and remove them from the exhaust gases

6.3.2.2. Spray Painting

6.3.2.2.1. Many mas produced object such as cars are spray-painted using electrostatic

6.3.2.2.2. To increase efficiency and reduce paint usage the paint particles and the car body are given opposite charges

6.3.2.2.3. This, the paint will be attracted to parts of the car not yet covered by paint

6.3.3. Dangers of Electrostatics

6.3.3.1. Lightning

6.3.3.1.1. Lightning is caused by charging produced by the friction between water droplets and air molecules

6.3.3.1.2. When the charge built up is large enough, the air will ionize allowing the charge to discharge to the ground

6.3.3.2. Fires and Explosions

6.3.3.2.1. Charges can build up on many objects such as planes and petrol tankers

6.3.3.2.2. If not discharged carefully, a spark can start a fire or cause an explosion

### 6.4. ELECTRIC FIELD

6.4.1. An electric field is a region where an electric charge experiences an electric force

6.4.2. It can be illustrated by drawing electric lines of forces

6.4.3. Properties

6.4.3.1. The lines can never cross each other

6.4.3.2. The lines behave as though they are under tension so they always ten to shorten their length

6.4.3.3. The lines repel each other sideways

6.4.3.4. The more closely spaced the lines, the stronger the force and the further apart the lines, the weaker the force