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STATIC ELECTRICITY Done By, Eugene Yeo (33) 4Engineering by
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STATIC ELECTRICITY Done By, Eugene Yeo (33) 4Engineering

Done By Eugene Yeo (33) 4 Engineering Physics Chapter 16 Static Electricity

LAW OF ELECTROSTATICS

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

Closer = Stronger

Further = Weaker

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

Like Charges, Positive + Positive, Negative + Negative

Unlike Charges, Positive + Negative

CURRENT

Electrical charges include electrons, protons and ions.

Electrons are Negative

Protons are Positive

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

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

The Symbol for Coulomb is Q

ELECTROSTATICS

Charging

Induction, Electrostatic charging is only for conductors, The charged object does not touch the sphere, The resultant charge on the sphere is opposite to charge of the inducing object, A ground is needed to create charge on the sphere or there will be no flow of electrons, The charges rearrange themselves in absence of charged inducing object, The direction of flow of elections is either from or towards the ground depending on the charge of the inducing object

Rubbing, Rub a balloon on the woolen sweater. Rub a glass rod on the silk scarf, Observations, When the balloon is placed near the pieces of paper, the pieces of paper are attracted to the balloon, When the glass rod is placed near the pieces of paper, the pieces of paper are attracted to it, When the glass rod is placed near the balloon, the glass rod is attracted to it, When two balloons are placed near each other, the balloons repell, When two glass rods are placed near each other, the glass rods repell, Explanaton, Before rubbing, the balloon and the glass rod were neutral in charge, By convention, charge obtained by rubbing glass with silk is positive and charge obtained when rubbing plythene with wool is negative, The balloons and glass rods were rubbed differently, so they must have opposite/unlike charges, The 2 balloons rubbed the same way should have the same/like charges, The 2 glass rods rubbed the same way should have the same/like charges, By the Law of Electrostatics, unlike charges attract, and like charges repell

Uses of Electrostatics

Flue-ash removal, Flue ash is a mixture of dust and smoke produced by many factories and power stations, Charged metal plates in the chimney attract these particles and remove them from the exhaust gases, Charged metal plates in the chimney attract these particles and remove them from the exhaust gases

Spray Painting, Many mas produced object such as cars are spray-painted using electrostatic, To increase efficiency and reduce paint usage the paint particles and the car body are given opposite charges, This, the paint will be attracted to parts of the car not yet covered by paint

Dangers of Electrostatics

Lightning, Lightning is caused by charging produced by the friction between water droplets and air molecules, When the charge built up is large enough, the air will ionize allowing the charge to discharge to the ground

Fires and Explosions, Charges can build up on many objects such as planes and petrol tankers, If not discharged carefully, a spark can start a fire or cause an explosion

ELECTRIC FIELD

Properties

The lines can never cross each other

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

The lines repel each other sideways

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