particle model of electrostatics:

Particle model of electrostatics:• Charge is a particle that is conserved – can’t be created or destroyed.

• Two kinds of charge - positive and negative / attraction and repulsion.

• Neutral objects have equal numbers of positive and negative charges.

• Only negative charges move.

• Two neutral objects can be charged by rubbing (friction) against each other – triboelectric charging.

• Charged object can charge neutral object by touching – conduction.

• Materials, which allow charges to move easily, are called conductors. Materials in which charges do not move easily are called insulators

4. Charge transferred to pith - same as rod. (repulsion)

1. Charged rod.

2. Charge separation in pith ball (attraction)

3. Pith touches rod – electrons move towards positives.

e-

Negative charge (excess e-)

Negative charge (excess e-)

CONDUCTION – with (-) rod

4. Charge transferred to pith - same as rod. (repulsion)

1. Charged rod.

2. Charge separation in pith ball (attraction)

3. Pith touches rod – electrons move towards positives.

e-

Positive charge (lost e-)

Positive charge (lost e-)

CONDUCTION – with (+) rod

Charging with NO contact:INDUCTION

• Demonstrate a temporary charge by induction.

• Demonstrate a permanent charge by induction.

• Explain how objects can be neutralized or charged by grounding.

KEY WORDSInduction Ground Grounding

Induction: A charged object is brought close to, but not allowed to touch, a neutral object producing an opposite charge in this object.

Charge separation is called a temporary charge induction.

Electrons move - causes temporary charge.

To place a permanent induced charge on an object requires grounding.

To “ground” an object means to connect the object and the Earth.

Earth easily absorbs or releases negative charges.

Electrons either flow up from the Earth into an object, or flow down from the object into the Earth.

Grounding also used to neutralize a charged object.

–––––

++

++

+

–

You connect to the Earth – ground by touching.

–––

– –

Neutralize positive OR negative objects.

–

4. Induced charge permanent – OPPOSITE as rod.

1. Charged rod is close – not touching.

2. Charge separation in object - GROUNDING

3. Electrons repelled towards Earth.

e-

Negative charge (excess e-)

Positive charge (lost e-)

INDUCTION – with (-) rod

4. Induced charge permanent – OPPOSITE as rod.

1. Charged rod is close – not touching.

2. Charge separation in object - GROUNDING

3. Electrons attracted from Earth.

e-

Positive charge (lost e-)

Negative charge (gained e-)

INDUCTION – with (+) rod

Triboelectric – by contact.• Two neutral objects are charged by friction.• One removes electrons off the other.• One becomes negative, other positive.

Conduction – by contact.• Neutral charged by touching a charged object.• e- jump to new object – charge separation.• Results in neutral object gaining the same charge.

Induction – no contact.• Charged object brought close to neutral object.• Ground causes permanent charge – due to separation.• Induced charge is always opposite of original.