RHSA SNC1D: Electricity

Charging By Contact – V2

Remember that when charging by friction both objects start with a neutral charge and end with opposite charges. After friction the oppositely charged objects attract each other.

When charging by contact one object starts with a positive or negative charge and the other object starts with a neutral charge. Then the positively or negatively charged object contacts the neutral object. The electrons are equally shared between both objects. After contact both objects will end up with the same charge. Then both objects will repel each other.


Ex. 1 A positively charged object contacts a neutral object

Draw BEFORE CONTACT between a positively charged wool sweater and a neutral cat.

Positive wool Neutral cat

8+ 4 - 8+ 8-

______

______


Ex.2: A negative object contacts a neutral object

Draw BEFORE CONTACT between a negatively charged rubber boot and neutral cotton.

Negative rubber Neutral cotton

8+ 12 - 8+ 8-

______

______


Charging By Contact – V2

Remember that when charging by ______both objects ______and ______. After friction the oppositely charged objects ______each other.

When charging by contact ______. Then the positively or negatively charged object contacts the neutral object. The electrons are ______between both objects. ______contact ______. Then both objects will ______each other.

Example 1: A positive object contacts a neutral object

Draw BEFORE CONTACT between a positively charged wool sweater and a neutral cat.

Example 2: A negative object contacts a neutral object

Draw BEFORE CONTACT between a negatively charged rubber boot and neutral cotton.


Charging by Contact Practice problems

Problem 1: A positively charged glass rod comes in contact with a neutral piece of wax. Draw before and after electrostatic diagrams showing the charges and the final charge on the objects.

Problem 2: A neutral platinum ring comes in contact with a negatively charged balloon. Draw before and after diagrams showing the charges and the final charge on the objects.

Homework: Read the lab description and look at the picture on p 276 to learn about a pith ball.

Read Nelson p 278-279. Do p 279 #1-4