When a charged object is brought near a neutral object, it causes (induces) the electrons to shift in position The induced movement of electrons in the neutral object by a nearby charged object is called an induced charge separation What happens to the electrons in the neutral ball when it is brought near a negative object?

What it is…  Vertical metal rod with 2 pieces of metal foil (leaves) that can detect static charge How it works…  Charge to be tested is applied to the metal ball (at the top)  When metal ball is touched with charged object, electrons are gained or lost from the leaves  This gain or loss of electrons causes each leaf to receive the same charge.  The leaves repel (because they share the same charge) *The greater the charge the farther the leaves spread apart

 A metal leaf electroscope can also be charged temporarily without touching it  Example: › if a negative charged object is moved near the metal ball (a), electrons in the ball repel the neg. object and move down into the leaves causing them to also become negative and repel against each other › When the charged object is moved away, the leaves return to their original positions (c) (induced separation)

› Electrostatic sprayers help reduce the amount of wasted paint › Electrostatic sprayers are especially useful for painting curved objects

This occurs when two objects of different amounts of electric charges come in contact and electrons move from one object to the other. BOTH OBJECTS END UP WITH THE SAME CHARGE! Example on board...

 We can charge an object by contact (conduction) – this involves taking a charged object and touching the neutral object to make it charged  ALSO we can charge a neutral object using a charged object BUT without making contact – this is called charging by induction.

 Recall when a charged object is brought near a neutral object it causes (induces) the electrons to shift position, resulting in an uneven distribution of electrons.

 Example: a negatively charged balloon is brought near a neutral wall.  Can you explain what happens?

 A neutral object can be permanently charged by induction by grounding the object. Which is process of connecting charged object to Earth’s surface  OBJECT being INDUCED ends up with the OPPOSITE CHARGE

 Fig. (a) a negatively charged bar is brought near a neutral ball.  The electrons in the ball are repelled by the negatively charged bar.  The ball becomes temporarily negatively charged on the right side

 Fig. b) attaching a ground wire to the ball conducts the repelled electrons on the right side into the ground.

 Fig. c) after removing the ground wire, the ball remains permanently positively charged.

 Charging by PERMANENT induction always results in two objects with opposite charges. (previous example: the bar is negative & the ball becomes positive).

 Suppose a car door handle becomes negatively charged. When you reach out to touch the door, you receive a shock.

 Objects with an excess electric charge, either positive or negative, can have the excess charge removed by a process called GROUNDING.  To ground an object it involves removing the excess charge by transferring electrons between the object and a large neutral object, such as the Earth (the ground )

When a positively charged object is grounded, electrons from the ground travel up to the positively charged object until it is neutral. When a negatively charged object is grounded, electrons travel from the object into the ground until the object is neutral.

 Part of the natural exchange process of electric charges between the atmosphere and the Earth  Very large electrical discharge caused by induction

 When these form, these negative charges gather at the bottom of the cloud  charge separation between the negative cloud and the positive Earth (tall building, tree) continues to build until it is large enough to ionize air molecules which allow them to become conductors

 Used to be called “friction machines” because used direct contact between different surfaces to create charged areas  Van de Graaf generator: use a roller and a belt to create friction and transfer charge to a large metal sphere

Read Section 10.2 Pages Complete on page 409 #’s 1-5, p.415 #2-4