Download Science 9: Electricity

Science 9: Electricity
Unit Review
*Know all vocabulary*
1. Identify and describe examples of mechanical, chemical, thermal, and
electrical energy.
2. Describe the energy transfers that take place in the following examples:
a. Power grids
b. Flashlights
c. Thermocouples
3. Why are electrodes and electrolytes necessary in a cell?
4. Which electrodes and electrolytes are best for use in a cell?
5. Explain the operation of a St. Louis motor.
6. How does changing the location of the armature, commutator and/or
magnets influence the operation of the St. Louis motor?
7. How can knowing the voltage and amperage of an electrical device keep
you safe?
8. What is the difference between static and current electricity? List some
examples of each.
9. List some examples of electrical conductors and insulators.
10. Which wire conducts electricity the best? The worst?
11. How does electrical resistance influence a polygraph (lie detector) tests?
12. What is a rheostat?
13. How can you use switches and/or resistance to control electrical flow?
14. Use a hydro-flow (water) model to explain current, resistance and voltage.
15. Calculate the resistance in the following examples using Ohm’s law:
a. What is the resistance of a light bulb of a 12V battery sends a
current of 2.4 A through it?
b. A toaster with a resistance of 145 () is connected to a 120 V
source. What current will flow through the toaster?
c. What is the potential difference across a 1500 () resistor carrying a
current of 0.075 A?
16. What are some problems associated with photoelectric cells?
17. What is the difference between a parallel circuit and a series circuit?
18. Which is the best to use when wiring a house, series or parallel? Why?
19. Identify the forms of energy input and output in a system.
20. Calculate the number of watts used in the following examples:
a. What is the power (in watts and kilowatts) of a hair dryer that
requires 10 A of current to operate on a 120 V circuit?
b. The maximum current that a 68.5 cm TV can withstand is 2A. If the
TV is connected to a 120 V circuit, how much power is the TV
using?
c. A flashlight using 2 1.5 V D-cells contains a bulb that can withstand
up to 0.5 A of current. What would be the maximum power of the
bulb?
21. Calculate cost of electrical usage in the following examples:
a. A family uses 3000 kWh of electric energy in a two month period. If
the energy costs 11.0 cents per kilowatts hour, what is the electric
bill for the period?
b. A home-owner finds that she has a total of 42 light bulbs (100 W) in
use in her home. If all the bulbs are on for and average of 5 h per
day, how many kilowatt hours of electricity will be consumed in a 30
day period? If electricity costs 11 cents per kilowatt hour, how
much will these lights cost her?
22. Identify examples of energy dissipation in the form of heat and describe
the effect of these losses on useful energy output.
23. Calculate the efficiency (compare inputs and outputs) of the following
examples:
a. Find the efficiency fo a 23 W fluorescent tube that is used 4.0h per
day and in that time produces 66 240 J of useful light energy.
b. A 80W incandescent bulb also produces about 66240 J over a 4 h
period. What is the efficiency of this light bulb?
24. What are some of the techniques that can be employed to reduce energy
consumption in your household?
25. How can you improve the efficiency of some common household devices?
26. Identify and evaluate alternative sources of electrical energy.
27. What are the by-products of electrical generation and describe their
impact on the environment?
28. What are some of the issues associated with electrical technologies in
storing and transmitting personal information?