Experiment 3 Charging by Contact and Induction In this experiment you will charge pith balls by contact and induction Materials Electrostatics Kit Masking Tape Monofilament Line Paperclip Wooden Block with Slit Metal Object ex Doorknob You Must Provide Procedure 1 Tear one small piece of masking tape from the roll approximately 5 cm 2 Create a small closed loop with the tape leaving the sticky side on the outside of the loop 3 Secure the looped tape to one of a side of the wooden block adjacent to the side with the slit 4 Press the taped side of the wooden block onto a smooth wall or the flat side of a counter or table top with the slit pointing perpendicular to the wall and parallel to the floor 5 Unwrap the outer layer of a paperclip 6 Use the exposed end of the paperclip to poke a hole through the centers of two pith balls 7 Thread one end of the monofilament line through one of the pith balls Tie a knot on the end that you threaded through to keep the pith ball on the thread Note If the paperclip created a larger hole three to five knots may need to be tied to secure the ball on the thread 8 Repeat Step 7 on the other end of the monofilament line with the other pith ball 2014 eScience Labs LLC All Rights Reserved 9 Once the pith balls are secured on each end of the line place the line in the slit of the wooden block The pith balls should rest at the same height 10 Remove any charge from the acetate strip wide and clear by grabbing it with your hand or rubbing it on a metal object like a door knob This is called grounding 11 Test for interactions between the acetate strip and both pith balls Record observations of any interaction 12 Charge the acetate strip by rubbing it with the cotton cloth 13 Slowly bring the plastic strip close enough to the right pith ball so that it moves but does not touch the plastic strip Once movement of the pith ball is observed move the plastic strip away Record your observations e g how far away were the two objects how fast did the pith ball move in what direction did the pith ball move etc 14 Slowly bring the plastic strip close enough to the left pith ball so that it moves but does not touch the plastic strip Once movement of the pith ball is observed move the plastic strip away Record your observations 15 Hold the monofilament line above the right pith ball and bring the ball into contact with the plastic strip 16 Let the pith ball hang again and bring the plastic rod close to but without touching the right pith ball What kind of interaction is observed Record your observations in Post Lab Question 3 17 Hold the line above the right pith ball and bring it close to the left pith ball Observe what happens Let the balls come into contact How does that change the interaction 18 Grab the pith balls to ground them and take away any charge they may have 19 Charge the plastic rod again with the cotton 20 Hold the line above the right pith ball with your pointer and middle finger Bring the right pith ball close to the plastic rod but do not let them touch This time touch the left side of the ball the one opposite of the rod with your thumb Let the ball hang again Bring the right pith ball close to the left pith ball Observe what happens Observations 2014 eScience Labs LLC All Rights Reserved Post Lab Questions 1 Explain why the pith balls were attracted to the charged plastic strip 2 State two observations that show the right pith ball was charged after it came into contact with the plastic rod 3 What did you observe as you performed Step 16 Use your results to explain what happened 4 Draw a diagram to show how Step 13 charged the right pith ball 5 What is the charge of each pith ball if they are attracted to each other Explain your reasoning 2014 eScience Labs LLC All Rights Reserved
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