introduction to electrostatics
TRANSCRIPT
MODULE 3: ELECTRICITY AND MAGNETISM
Electrostatics
ElectrostaticsThe study of the effect that charges
in rest have on each other
Objects become
charged by gaining or
loosing electrons
Introduction
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Two types charges:
Positive:Shortage of Electrons
Negative:Excess of Electrons
Protons and neutrons cannot be
transferred!!!
IntroductionForces between charges:
Like charges repel each other
Opposite charges attract each other
Charging objectsFriction
Electrons are transferred when two objects are rubbed against each other
Charging objectsTouch
Electrons are transferred when a charged object touches a neutral object
Charging objectsInduction (polarization)
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Charged particles in a neutral object rearrange when a charged objects is
brought close to it
Causes temporary charge distribution so neutral object can be attracted
Charging objectsInduction (polarization)
Conservation of ChargeCharge cannot be created or
destroyed, but only transferred from one object to another.
Conservation of Charge
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-2 nC -4 nC
Charge distribute equally among both
spheres
Conservation of ChargeCalculate new charge on spheres
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-2 nC -4 nC
𝑄 𝑓=𝑄1+𝑄2
2
𝑄 𝑓=−2+(−4)
2𝑄 𝑓=−3𝑛𝐶
-3 nC-3 nC
Quantisation of ChargeNumber of electrons
∆𝑸=𝑸 𝒇−𝑸𝒊
𝒏𝒆=∆𝑸𝒒𝒆
Where = Charge Transferred(C)= Initial Charge (C) = Final Charge (C)= Number of Electrons= Charge of Electron= C
Example 1Two identical metal spheres have different charges. Sphere A has a charge of -5 nC.
Sphere B has a charge of 3 nC.
a) What is the nature of the force between A and B?
b) If the two spheres touched, what will the new charge on the spheres be?
c) What is the new nature of the forces between sphere A and sphere B?
d) In which directions were the electrons transferred?
e) How many electrons were transferred?
Example 2Two identical metal spheres have different
charges. Sphere A has a charge of –96 X 10-18 C. Sphere B has 60 excess
electrons.
a) What is the charge on sphere B?b) If the two spheres touched, what will
the new charge on the spheres be?c) How many electrons were transferred?