LAB: INVESTIGATING STATIC ELECTRICITY

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PLEASE FILL THE BLANKS/ THIS IS AN INDIVIDUAL WORK.

A BLANK NOT FILLED = -5%. TRY TO BE NEAT.

PLEASE BE RESPECFULOF THE MATERIALS. SOME ARE FRAGILE.

PURPOSE

 

Investigate the behavior of static electricity

 

DISCUSSION, FILL THE BLANCKS FOR FULL CREDITS

( use words as: negatively, positively, positive, negative, electrons, ground,  rubbed, charges)

 

As seen in the movie, clothes removed from the dryer usually cling to each other and spark or crackle with static electricity when they are separated, When 2 dissimilar materials are ______________ together they can become _____________. Object can acquire static electric charges by either gaining or losing _____________. An object that gains ___________ has a net _________ charge and is said to be ______________ charged. An object that loses _____________has a net _____________ charge and is said to be ___________ charged. Only those objects separated from a ground or Earth, by an insulator will retain their charge for any length of time (capacitor or leyden jar can hold charges). Objects that are attached to the _________ through a conductor will remain uncharged, since the charge travels into the ___________ and is quickly dissipated.

 

Remember the affinity chart ?

Hold electrons tightly
brass
copper
ebonite (rubber)
wax
silk
lead
fur
wool, fur
glass
hold electrons lightly

According to this chart if you rub a hard rubber rod with wool or fur, the rod will become _____________ charged. Whereas, if you rub a glass rod with silk, the glass rod becomes ____________ charges. In this experiment, you will charge object and observe their interactions with other charges objects.

 

Materials

 

Hard rubber rod                                 wool pad

Glass rod                                            pith ball suspended by silk thread from holder

Plastic wrap or acrylic rod                 leaf electroscope

Silk pad                                              leyden jar                                       wire with alligator clip

 

Procedure

 

Try to perform the experiment in a cool dry day. (humidity take the charges away). You may have to be energy when rubbing the rods. Don’t hesitate to do an experiment several times. Take turn.

 

 

Part I: Negatively charging a pith ball

 

Step1: Rub the hard rubber rod with the fur or wool pad to charge it. Bring the rod close to,

BUT NOT TOUCHING, a suspended pith ball, as shown in figure (right). Observe the behavior of the pitch ball and record your observations in Table1. Touch the pith ball with your finger to remove the any charge it may have (grounded).

Step2: Charge the robber rod again. Bring it close to the pith ball and allow it to touch the ball. Then bring the charged rod near the charged ball and observe the behavior of the ball. Record your observation in TABLE 1.

Part II: Positively charging a pith ball

 

Step1: Rub the glass rod with a piece of silk to charge it. Bring the rod close to, BUT NOT TOUCHING, a suspended pith ball. Observe the behavior of the pith ball and recode your observation in TABLE 2. Touch the pith ball with your finger to remove any charge any charge it may have.

Step2: Charge the glass rod again. Bring it to the pith ball and allow it to touch the ball. Then bring the charged rod near the charged ball and observe the behavior of the pith ball. Record your observations in TABLE 2.

Step1 : NOT TOUCHING !

Part III: Charging an electroscope by conduction

 

Step1: Look at the leaf electroscope or a vane electroscope that you will be using an familiarize  yourself with its responses to static charges. Charge the rubber rod with the fur or the wool. GENTLY bring it in contact with the top of the electroscope. The electroscope is now negatively charged. Observe what changes take place in the electroscope. Record your observations in TABLE 3.

Step2: Recharge the rubber rod (fur). Bring it near the charged electroscope (NOT TOUCHING
) Observe what changes take place to the leaves or the vane. Record your observations in TABLE3.

Step3: Recharge the electroscope with a negative charge (step1) from the rubber rod (and fur). Charge the glass rod (silk) and bring it near the top of the negatively charged electroscope (NOT TOUCHING). Observe the electroscope deflections as the charged rod is moved close to and away fro the electroscope. record your observations in TABLE3. Discharge the electroscope by momentarily touching the top of it with your finger.

Step4: Charge the plastic wrap or acrylic rod with a piece of silk. Touch the plastic material to the top of the electroscope to charge it. Set the plastic material aside. Charge the rubber rod (fur) and bring it near to the electroscope while observing the deflections of the leaves or vane. Record your observations in TABLE3. What type of charges is on the electroscope ?

 

 

 

 

 

 

PART IV: charging a leyden jar

 

Step1: Place a Leyden jar beside the electroscope

Step2: Charge one of the rods and gently touch the electroscope to charge it. Repeat the procedure to place a fair amount of charge and to cause a large deflection

Step3: Discharge the electroscope by touching the top with your finger. Use the clip wire to attach the top of the electroscope to the top of the leyden jar (see figure). Note that the leyden jar is not grounded. Repeat step2 and find out if there is any difference in the ability of the electroscope to be charged? Record observations in TABLE4.

PART V : charging an electroscope by induction

 

Step1: Charge one of the rod (positively or negatively, depending on the type of rod). Bring the rod  near the electroscope within 1-2cm. NOT TOUCHING the electroscope. Observe the leaves or vane. Record your observation in TABLE5 .

Step2: With the charged rod near the electroscope, touch quickly the top of the electroscope with a finger. Remove your finger and remove the rod. Observe the leaves or vane. Record observations in TABLE5.

Step3: Following the procedure in part 3. determine the type of charge on the electroscope. Record your observation in TABLE5. (if a + charged is brought near a + charged electroscope, you should see more deflection. If a + charged rod is brought near a - charged electroscope , you should see less deflection). With your finger you grounded the electroscope, getting rid of the + or - charges. It is another way to charge the electroscope negatively or positively