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Quarter 4 Benchmark Study Guide ANSWER KEY
1. An electric field is the space around a particle through which an electric charge can exert a force.
2. A short, thick, copper wire would have a lot less resistance than a long, thin, copper wire.
3. Give an example of technology that uses static charges. Photo copier
4. An ampere is the standard unit of measure for current.
5. In a “dead” household battery the chemical reactions inside the cell have stopped.
6. Induction is the build up of charges without contact.
7. Give an example of static charges that build up through contact. Walking across carpet in rubber shoes.
8. Positive charge building up on the ground before lightning flashes is an example of induction
9. An electric charge will move between two positions with different potentials.
10. Give an example of charging by induction before a flash of lightning, positive charges building up on the
ground’s surface.
11. An electric current is a flow of charge.
12. Lightning strikes a lightning rod instead of a house because the rod has a lower resistance than the house.
13. When you walk across carpet and then touch a conductor you might feel a shock.
14. Wire made of a material with low resistance might be used in a power line.
15. If two particles that have the same electric charge come into contact what will happen? They will repel.
16. An object with no net charge will become charged when it touches another neutral object that gives
electrons to it.
17. Fabric softener reduces static charge on clothes in order to prevent them from sticking together.
18. If a charge moves between 2 objects what can you conclude about the potentials of the 2 objects? There is a
potential difference between the two objects.
19. Voltage increases as the difference in electrical potential between two points increases.
20. Wires with a high electrical resistance are typically used in a light bulb.
21. What is the formula for Ohm’s law? Current = voltage / resistance or I = V / R
22. According to Ohm’s law, electric current increases when voltage increases or resistance decreases.
23. How are storage cells recharged? Chemical reactions that produce current are reversed.
24. Do electrons leave a battery cell from the negative terminal or the positive terminal? Negative termanil
25. Are primary cells rechargeable? No
26. Name three factors that will affect how long a batter will last. How often the battery is used, how much
power the light bulb uses, how long the battery is used.
27. Suppose a power line falls onto the ground near a car. Would it be safe for a person to approach the car?
Explain. No, the ground conducts the charge from the power line in every direction. Thus, a person can
get a deadly shock from the ground.
28. Write one sentence to compare and contrast each of the following terms
Electric current and static discharge both are the movement of charge and static discharge is limited while
electric current is a continuous flow of charges.
Conductor and insulator are both materials that allow electric charges to pass through them; conductors
allow the charge to pass easily while insulators slow the flow of charge.
Primary cells and storage cells are both electric cells that produce electric current; primary cells produce
current by chemical reactions until the reactants are used up, and storage cells produce current by way
of chemical reactions that can be reversed inside the cell.
29. After a balloon is rubbed against a wool sweater, the balloon will temporarily stick to a wall. Draw and
label a picture showing what has happened to the electrons in the balloon and the wall, and write 4 sentences
to explain why this happens. (use these terms – negative charge, electrons, unlike charges, and positive
charge)
Electrons travel from the wool to the balloon, which develops a negative charge. When the balloon is
placed on the wall, the wall’s electrons shift away from the balloon’s negative charge. This electron shift
leaves a positive charge on the wall near the balloon. The unlike charges of the balloon and the wall’s
surface attract.