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Name: __________________________________________ Block: _________ Date: _________________
Chapter 17 Study Guide key
1. How does an atom become positive? How does an atom become negative?
An atom becomes positive by loosing electrons and negative by gaining electrons.
2. Explain the parts of an atom. What charges do they have? Why can the electrons move out of the atoms but not
the protons? Protons are positively charged and Neutrons have no charge. They are both found in the nucleus
in the center of the atom. Electrons have a negative charge and are located on the outside of the nucleus on the
outside of the atom.
3. Explain the difference between an electric field and an electric force.
An electric field is the region of influence a charged particle has and an electric force is the push or pull between
two charged particles.
4. What does the electric force do to two objects that have opposite charges? What does the electric force do to
two objects with positive charges? An electric force attracts two objects with opposite charges and repels two
objects with positive (or both negative) charges.
5. What does the size on an electric force depend on?
The size of an electric force depends on the size of the charges and the distance between them.
6. What instrument can we use to detect a charge? How does it work?
A charge may be detected with an electroscope. As a charged object is placed near the electroscope the electrons
on the metal ball will either gather on the ball (if the charge is positive) or move away from the ball (if the
charged object is negative). Furthest away from the ball are two foil pieces that have the opposite charge of the
ball. Since both foil pieces have the same charge they repel and spread out.
7. Give two examples of conductors and two examples of insulators.
Two examples of conductors are tap water and metal. Examples of insulators include plastic, glass and rubber.
8. Describe the three ways an object can become charged.
An object may be charged by friction (rubbing two insulators together such as a balloon on your head), induction
(charging an object without touching as with Q. 6 above), or by conduction (by direct contact such as by a wire).
9. Explain how the clothes in the dryer build up static electricity.
As two insulators rub together electrons from one object get pulled on the other object leaving one with more
electrons (creating a negative charge) and the other with less electrons leaving more protons (creating a positive
charge).
10. What is similar about the shock we feel from touching something metal and a lightning bolt? What is different
about them?
Both touching metal and a lightning bolt are examples of a static discharge, but lightning has a larger discharge.
11. Explain the difference between a dry cell and a wet cell. Give an example of each type.
Dry cells such as a D-cell battery have a dry or paste-like electrolyte while a wet cell uses a liquid electrolyte and
were used for automobile batteries.
Electrode (2 different
Wire
12. Draw and label a wet cell.
metals)
Electrolyte (Liquid or
paste-like material)
Name: __________________________________________ Block: _________ Date: _________________
13. Explain how a cell produces an electric current.
A chemical reaction takes place between the electrodes and the electrolyte that puts additional electrons on the
zinc electrode and removes them from the copper electrode. The difference between the charges causes charges
to flow across the wire.
14. Why does a flashlight battery stop working after a while?
As the battery is used negatively charged electrons move to the positive terminal with a positive charge (fewer
electrons). After usage both terminals have less charge which is a decrease in the potential difference.
15. What is another word for potential difference? How can the amount of potential difference be increased? What
is the unit for potential difference?
Voltage is another word for potential difference. It can be increased by adding cells & it is measured in Volts (V).
16. Name two other ways besides chemical energy to produce electrical current. Give examples.
Photocells create current from solar energy and thermocouples produce electrical energy from differences in
temperature.
17. In your own words, explain what a current is. What is the unit for current?
Current is the movement of charges and is measured in amps (A).
18. Explain the difference between direct current and alternating current. Give examples of each type.
Current from batteries is direct current (DC) and it moves in one-direction. Current from outlets is called
alternating current ( AC) and it changes or alternates its direction of movement.
19. Explain what thickness, length and temperature would be for a very high resistance wire and a low resistance
wire.
Thick, short and cold wires have low resistance while thin, long and hot wires have high resistance.
20. Using the above information about resistance, explain why a light bulb has a very thin wire.
A light bulb is created to produce light and it can only do with is the resistance is high enough to make it glow.
21. What three things must you have for a circuit? What may you have as part of a circuit?
A circuit must have an energy source, at least one load, and wires to connect them. Circuits may also have
switches, fuses or circuit breakers for convenience and safety.
22. Draw the two types of circuits. Which would you use in your home and why?
See sketches in notes. At home I would use parallel circuits so that the power wouldn’t go out everywhere on a
circuit when a light bulb went out.
23. What happens to the brightness of the light bulbs when you add more to a series circuit and a parallel circuit?
The brightness of light bulbs in series decreases as bulbs are added. In a parallel circuit each added bulb retains
its full brightness.
24. If one light bulb blows out in a series circuit, do the others stay on? Why or why not?
If one light bulb blows out in a series circuit the others turn off because the filament is broken, which opens the
circuit.
Name: __________________________________________ Block: _________ Date: _________________
25. If one light bulb blows out in a parallel circuit do the others stay on? Why or why not?
If one light bulb blows out in a parallel circuit the others stay on because there are other paths for the current to
travel.
26. What is the difference between an open circuit and a closed circuit?
An open circuit is where a switch is open which cuts the path and shuts it off. A closed circuit has the switch
down allowing charges to move across it and allows the circuit to turn on.
*** Review your Ohm’s Law calculations!! Also look over your quiz, notes and other worksheets ***