# STATIC ELECTRICITY II: Charging neutral objects. S1-3-07 Construct one or more electrostatic apparatus and explain how they function using the particle.

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STATIC ELECTRICITY II: Charging neutral objects

S1-3-07 Construct one or more electrostatic apparatus and explain how they function using the particle model of electricity. KEY WORDS ElectroscopeGrounding ConductionInduction

Electroscope: a tool for determining whether or not an electrical charge is present in an object. It provides 3 kinds of measurement: – detects the presence of a charge – determines the type of charge (+ or – ) – determines the amount of charge We will look at two kinds of electroscopes: pith ball and foil leaf

Polarization is NOT permanent – when the charged object moves away – electrons move back to neutral, leaves close Leaf Electroscopes

Polarization is “inducing” a temporary charge A permanent charge can be placed on an object by: 1.Conduction – charging by contact 2.Induction – charging with grounding 1. Conduction Electric charge transfers from a charged object to a neutral object by touching End result: the neutral object gains the same charge as the object

END: Both objects are overall (-) charged (repulsion) 1. Charged rod 2. Polarization in pith ball (attraction) 3. Pith touches rod – electrons are transferred e-e- Negative charge (excess e - ) Negative charge (excess e - ) (–) CONDUCTION

END: Both objects are overall (+) charged (repulsion) 1. Charged rod 2. Polarization in pith ball (attraction) 3. Pith touches rod – electrons are transferred e-e- Positive charge (lost e - ) Positive charge (lost e - ) (+) CONDUCTION

Polarization is “inducing” a temporary charge 1. Induction Grounding is used to place a permanent electric charge on a polarized neutral object End result: the neutral object gains the opposite charge as the object The charged object and neutral object DO NOT make contact

– –––– + + + + + – – – – – – – Grounding is used to “reset” or neutralize a charged object To “ground” means connect the object to Earth: Electrons move up from Earth into an object, or move down from the object into Earth (as needed)

END: Objects have overall opposite charge 1. Charged rod is close – not touching 2. Polarization in object - GROUNDING 3. Electrons repelled off towards Earth e-e- Negative charge (excess e - ) Positive charge (lost e - ) (–) INDUCTION

END: Objects have overall opposite charge 1. Charged rod is close – not touching 2. Polarization in object - GROUNDING 3. Electrons attracted over from Earth e-e- Positive charge (lost e - ) Negative charge (gained e - ) (+) INDUCTION

Triboelectric – by friction START: two neutral objects friction causes electron transfer END: one becomes (-) charged, other (+) charged Conduction – by contact START: neutral object and a charged object polarization and then contact causes electron transfer END: Both objects have the same charge Induction – with grounding START: Charged object brought close to neutral object polarization and then grounding causes electron transfer END: Both objects have the opposite charge

CAN YOU ANSWER THESE QUESTIONS? S1-3-07: How does an electrostatic apparatus work to identify charge? KEY WORDS ElectroscopeConduction InductionGrounding

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