Material Needed

• A roll of invisible tape, such as Scotch brand MagicTM Tape or a generic brand. It must be the kind of tape that almost disappears when you smooth it down on a surface, not ordinary cellophane tape.
• Two books or other objects to suspend a tape in between
• One balloon
• Two different types of sweater, if possible one from natural wool and another one from synthetic materials

How to make a U Tape Use a strip of tape about 20 cm long (about 8 inches, about as long as a letter-size paper is wide). Shorter pieces are not flexible enough, and longer pieces are difficult to handle. Fold under one end of the strip to make a non-sticky handle, as shown in the Figure.

• Stick a strip of tape with a handle down onto a smooth flat surface such as a desk. This is a "base" tape.
• Smooth this base tape down with your thumb or fingertips.
• This base tape provides a standard surface to work from. (Without this base tape, you get different effects on different kinds of surfaces.)
• Stick another tape with a handle down on top of the base tape, as shown in the figure.

• Smooth the upper tape down well with your thumb or fingertips.
• Write U (for Upper) on the handle of the upper tape.
• With a quick motion, pull the U tape up and off the base tape, leaving the base tape stuck to the desk.
• Hang the U tape vertically from the edge of the desk, and bring your hand near the hanging tape, as shown in the figure.

• If the tape is in good condition and the room is not too humid, you should find that there is an attraction between the hanging strip of tape and your hand when you get close to the tape.If there is no attraction, remake the U tape.

Experimental technique:try to handle the tapes only by their ends while you are doing an experiment. Interaction of two U tapes

(a) If U tapes are electrically charged, how would you expect two U tapes to interact with each other? Would you expect them to repel each other, attract each other, or not to interact at all? Make a prediction, and briefly state a reason. (b) Make two U ("upper") tapes by following the procedure detailed above. Make sure that both tapes interact with your hand. Hang one on the edge of a desk. Bring the second U tape near the hanging U tape. Since the hanging tape is attracted to your hands, try to keep your hands out of the way. For example, you might approach the vertically hanging tape with the other tape oriented horizontally, held by two hands at its ends. What happens?

You should have seen the two U tapes repel each other. If you did not observe repulsion, try remaking the U tapes (or making new ones, both from the same roll of invisible tape).

How to make an L Tape

• Stick a new strip of tape, with a handle at one end, down onto a base tape that is stuck down on the desk. Smooth it down with your thumb or fingertips, and write L on its handle. Then stick another strip with a handle on top of the L tape, smooth it down, and write U on its handle.

• You now have three layers of tape on the desk: a base tape, an L tape, and a U tape as shown in the figure.

• Slowly lift the L tape, bringing the U tape along with it (and leaving the bottom base tape stuck to the desk). Hang the double layer of tape vertically from the edge of the desk and see whether there is attraction between it and your hand (see the figure). If so, get rid of these interactions (hold the bottom of the tape and slowly rub the slick side with your fingers or thumb).
• Check that the tape pair is no longer attracted to your hand.THIS IS IMPORTANT!
• Hold onto the bottom tab of the L tape and quickly pull the U tape up and off (see the figure). Hang the U tape vertically from the edge of the desk, not too close to the L tape!
• Repeating exactly the same procedure, make another pair of tapes so that you have at least two U tapes and two L tapes. Before separating the two tapes from each other, remember to run your finger along the slick side of the tape pair to get rid of interactions with your hand.

Interaction of two L tapes

(a) If L tapes are electrically charged, how would you expect two L tapes to interact with each other? Would you expect them to repel each other, attract each other, or not to interact at all? Make a prediction, and briefly state a reason. (b) Hang one L tape on the edge of a desk. Bring the second L tape near the hanging L tape. Since the hanging tape is attracted to your hands, try to keep your hands out of the way. For example, you might approach the vertically hanging tape with the other tape oriented horizontally, held by two hands at its ends. What happens?

You should have seen the two L tapes repel each other.If you did not observe repulsion, try remaking the L tapes (or making new ones, both from the same roll of invisible tape).

Interaction of a U with an L tape

(a) If U and L tapes are electrically charged, how would you expect a U and an L tape to interact with each other? Would you expect them to repel each other, attract each other, or not to interact at all? Make a prediction, and briefly state a reason. (b) Suspend the one type of tape between two books and lower the oppositely charged tape toward it. What will happen to the tape suspended between the two books? Make a prediction, and briefly state a reason.

You should have seen the U and the L tape attract each other.If you did not observe attraction, try remaking the U and the L tapes (or making new ones, both from the same roll of invisible tape).

Interaction of a U and/or L tape with a balloon and other materials

• Blow air into the balloon that it is big, but not too big that it will pop when you touch it too hard
• Tie the balloon so that the air cannot escape
• Rub the balloon against a sweater

Q1. Bring the balloon towards a hanging U tape and make sure that the balloon and the tape do NOT touch - what do you observe? Q2. Now, bring the balloon towards a hanging L tape and make sure that the balloon and the tape do NOT touch - what do you observe?

• Rub the balloon against another type of sweater

Q3. Bring the balloon towards a hanging U tape and make sure that the balloon and the tape do NOT touch - what do you observe? Q4. Now, bring the balloon towards a hanging L tape and make sure that the balloon and the tape do NOT touch - what do you observe? Q5. Take a U tape and bring it close to the first sweater - what do you observe? Q6. Take an L tape and bring it close to the first sweater - what do you observe? Q7. Take a U tape and bring it close to the second sweater - what do you observe? Q8. Take an L tape and bring it close to the second sweater - what do you observe?

The two basic principles behind static electricity that you experienced in the sticky-tape exploratory lab are

• Like charges repel
• Unlike charges attract

There are two types of charges, namely

• negative charges: the smallest negative charge is on the electron
• positive charges: the smallest positive charge is on the proton

The charge on the proton and the charge on the electron are the same in magnitude, but they have opposite signs. Aneutral objecthas the same amount of positive charges as it has of negative charges. Objects canacquire static charges through friction(rubbing the balloon against a sweater)or manual separation(in the sticky-tape portion of the lab). Either case results in an object that is no longer charge neutral, but has either lost some electrons and is therefore positively charged or gained some electrons and is therefore negatively charged. When you take an electrostatically charged balloon and place it near a wall it will be attracted to the wall, although the wall is not charged. However, the molecules in the paint orient themselves in the following manner

The phenomenon where the object rearranges its charges but remains overall charge neutral is calledcharging by induction.

Q9. There are several everyday life situations where we experience this electricity - now we can be more precise and say it is static electricity. Give two examples of everyday life experiences that you can think of and that were not covered here. Describe whether the charging is due to friction, charge separation, or charging by induction. Q10. Do some research to find out how to show charging by induction using a comb, or another plastic item, and water. Q11. Place a dry mixture of salt and pepper in a clear plastic bag. Take a plastic spoon or knife and rub it against a sweater or towel. Bring the plastic spoon or knife close to the plastic bag with salt and pepper. What do you observe? What is the explanation of what you observe?

Q12. Find out which materials are good insulators and describe two of these materials and their applications here. Q13. Find out which materials are good conductors and describe two of these materials and their applications here. Q14. Find out what the term semiconductor means and explain it. Find out which materials are semiconductors and describe two of these materials and their applications here.

Q15. Define the following terms:

1. Voltage
2. Resistance
3. Current
4. Ohm's Law

Q16. What are the units for the following electric quantities: voltage, current, and resistance. Q17. If you connect a resistor with a resistance of 10 Ohm to a 1.5-V battery, what will the current be that is flowing through this resistor? Show calculation.