ELECTROSTATICS QUICK GUIDE AP Physics 1 ELECTROSTATICS Electrostatics

ELECTROSTATICS • Electrostatics deals with charges objects that are at equilibrium or point charges

ELECTROSTATICS • Charge must be conserved, so the charge transferred to one object must

ELECTROSTATICS • Objects are charged through various methods: • Conduction – direct contact and

ELECTROSTATICS • Charging by conduction • Electrons will move from a more negative object

ELECTROSTATICS • Charging by induction • A charged object may be placed near, but

ELECTOSTATICS • Excess charge • Conductors – charge is distributed evenly at the surface

ELECTROSTATICS • Electric force example • Two charges of magnitude Q are placed a

ELECTROSTATICS • Summary • Electrons transferring are the cause of charging objects • If

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ELECTROSTATICS QUICK GUIDE AP Physics 1

ELECTROSTATICS • Electrostatics deals with charges objects that are at equilibrium or point charges interacting with one another. • Objects obtain a net charge through the transfer of electrons. • Positive objects are due to a loss of electrons.

ELECTROSTATICS • Charge must be conserved, so the charge transferred to one object must be equal to the charge transferred from another object. • Example: a neutral balloon is rubbed with a neutral piece of fabric. The balloon obtains a charge of -2. What is the charge of the fabric? +2 • Net charge had to be 0 before and after

ELECTROSTATICS • Objects are charged through various methods: • Conduction – direct contact and transfer of electrons • Induction – no transfer of electrons; may rearrange charges within an object though.

ELECTROSTATICS • Charging by conduction • Electrons will move from a more negative object to a less negative object until both objects have the same charge. • Example: A negatively charged object is allowed to touch a neutral conducting sphere. Electrons will transfer to the neutral object giving it a negative charge that will eventually be the same as the other object.

ELECTROSTATICS • Charging by induction • A charged object may be placed near, but not touching another object. This will rearrange the charges based on whether the electrons will attract towards or away from the charged object. • Example: A positively charged object is placed near a neutral conducting sphere. Electrons in the sphere will attract to the side closet to the positive object. This leaves the opposite side with a positive charge; however, the sphere is still neutral since no transfer of charge among objects occurred.

ELECTOSTATICS • Excess charge • Conductors – charge is distributed evenly at the surface of a conductor • Insulators – excess charge is at the point of transfer. Insulators may have a net charge, but the electrons are not free to move and spread throughout the insulator.

ELECTROSTATICS •

ELECTROSTATICS • Electric force example • Two charges of magnitude Q are placed a distance D from one another. The electric force is measured as F. • Suppose one of the charges doubles in magnitude and the distance between the charges is doubled. In terms of F, what is the new electric force between the charges? F/2 • Doubling one charge would double the force, but doubling the distance reduces the force by a factor of 4. The resulting change is the force is ½ the original force.

ELECTROSTATICS • Summary • Electrons transferring are the cause of charging objects • If no electrons are transferred, then an objects net charge does not change, but charges within the object may have been rearranged. • Objects in contact will transfer electrons until equilibrium is reached (same charge). • Charges are free to move in conductors.