Charging by Contact and by Induction

# Charging by Contact and by Induction

## Charging by Contact and by Induction

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##### Presentation Transcript

1. Charging by Contact and by Induction

2. Detecting Charges • Electroscope: A device that detects the presence of electric charges • Pith Ball Electroscope: A small light conductive ball suspended by a cotton thread • When a charged object is brought near the pith ball, it causes it to move • Metal leaf electroscopes have a sphere connected to a rod with metal leaves attached to it (all made of metal). • The leaves spread apart when a charge is near the sphere

3. Charging by Contact • Takes place when contact is made between a neutral object and an object that is charged • On contact, electrons flow from the negatively charged object into the pith ball • After contact, both the object and pith ball have a negative charge

4. The Laws of Electric Charges • An object may be electrically neutral, negatively or positively charged • The charge on an object is determined by the electrons (they can move from one object to another) • 3 Laws: Like charges repel, opposite charges attract and charged and neutral objects attract each other

5. The Amount and Type of Charge • Amount of charge depends on the difference between the number of protons and electrons • The size of the electric force is directly proportional to the amount of charge on each object • As the distance between two charged objects increases, the electric force decreases • To determine if an object is charged and what type of charge, you must observe repulsion between it and another object

6. Electric Fields • Electric Field: An electric force that exists between two objects that are not in contact if at least one of them is charged • Objects with greater charges have stronger electric fields • electric forces are transmitted at the speed of light

7. Charging by Induction • When a charged object is close to a neutral one, the electric field of the charged object produces a force on the neutral object - the force is attractive • Induced Charge Separation: The movement of electrons in a substance caused by the electric field of a nearby charged object without direct contact between the substance and the object