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Electricity Ch 1 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. What is the formula for Ohm’s law? Current = voltage / resistance or I = V / R
20. How are storage cells recharged? Chemical reactions that produce current are reversed.
21. Do electrons leave a battery cell from the negative terminal or the positive terminal? Negative terminal
22. Are primary cells rechargeable? No
23. When a circuit is closed a continuous charge flows.
24. A fuse is a protective device that breaks a circuit when too much current flows through it.
25. The set up of the circuits in an appliance partially effects the function that an electrical appliance can
perform.
26. A switch, opens and closes the path of charge in a circuit.
27. Current follows a closed path in every circuit.
28. If you change a light bulb in a lamp, what part of the circuit are you changing? The resistor
29. A short circuit is an unintended path connecting one part of a circuit with another.
30. Give an example of a short circuit a wire melts in a fan and accidentally forms an unplanned circuit.
31. The part of a circuit that opens and closes the circuit path is the switch
32. A switch turns off a light because it closes the circuit.
Show ALL work for number 33-34
33. A 360-volt air conditioner has a resistance of 6 ohms. What is the current?
I = V/R
I = 360V / 6 Ohms
I = 60 Amps
34. An electrical pathway has a current of 10 amperes and resistance of 400 ohms. What is the voltage?
V= I x R
V = 10 A x 400 Ohms
V = 4000 Volts
35. 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 through induction.
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.
36. Draw and describe the four parts of a basic circuit: voltage source, conductor, switch, and electrical device.
A voltage source supplies the electric potential for charge to flow through a circuit. A conductor, such as
a wire, must form a connection from the voltage source to the electrical device and back. A switch can
open a circuit to stop the flow of charge and close a circuit to allow a charge to flow. An electrical device
is something that changes electrical energy into another form of energy.