Charging Neutral Objects

• Electric charge can be influenced to move by the presence of other charges (same or different)

• To charge a neutral object, electrons need to be added or removed (Why electrons?)

1. Conduction:charging by contact between a charged object and a neutral object

= += -

NeutralCharge = -6e

1. Conduction:charging by contact between a charged object and a neutral object

= += -

Charge = -1eCharge = -5e

1. Conduction:charging by contact between a charged object and a neutral object

= += -

Charge = -2eCharge = -4e

1. Conduction:charging by contact between a charged object and a neutral object

= += -

Charge = -3eCharge = -3e

1. Conduction:• Once the charges on the objects have equalized, no more

charge is transferred.

• The overall (net) charge is still -6e because charge is conserved

= += -

Charge = -3eCharge = -3e

2. Induction:• This method involves no direct contact

between the charged and neutral objects

• Charges in the neutral object are influenced by an external electric field, but no transfer occurs with the charged object

2. Induction:Start with two neutral conductors (this won’t work very well with insulators) that are in contact with each other but are not grounded

= += -

2. Induction:Bring a charged object near the two conductors, but do not make contact with either conductor

= += -

both are neutralcharge = -3e

2. Induction:The charged object pushes electrons from the right-hand sphere to the left-hand sphere

= += -

charge = -3e

2. Induction:The charged object pushes electrons from the right-hand sphere to the left-hand sphere

= += -

charge = -3e

2. Induction:The charged object pushes electrons from the right-hand sphere to the left-hand sphere

= += -

charge = -3e

2. Induction:Now separate the two spheres while the charged object is still nearby

= += -

charge = -3e

2. Induction:Now separate the two spheres while the charged object is still nearby

= += -

charge = -3e

2. Induction:Now separate the two spheres while the charged object is still nearby

= += -

charge = -3e

2. Induction:Remove the charged object and notice that…

= += -

…the left-hand sphere has three extra electrons (charge = -3e)

and the right-hand sphere has lost three electrons (charge = +3e)

2. Induction:Both objects are now charged although neither made contact with the charged object!

= += -

• The overall (net) charge is still zero since charge is conserved.

• All charge gained by one is lost by the other!

charge = -3e charge = +3e