The power source

1. Tightly wrap about a metre of the wire around an empty paper tube and secure in place with tape.
2. Leave about 20 cm of wire free at each end of the tube.
3. Remove about 1 cm of insulation from each end of the wire.
4. Use the bar magnet to produce an electrical current by moving it several times in and out of the centre of the paper tube. You will need to build the accompanying "detecting device" to prove that current is being generated.

The detecting device

1. Tightly wrap two metres of wire around a drinking glass and secure in place with tape.
2. Leave 15 cm of wire free at each end.
3. Remove about 1 cm of insulation from each end of the wire.
4. Place the compass inside the glass.
5. Connect the wire ends of the "power source" to the wires of the "detecting device".
6. Push the bar magnet in and out of the paper tube several times. What happens to the needle of the compass?

Thermostats

Thermostats, introduced in the late 1920s, were an extremely important addition to many household appliances such as irons, stoves, heaters, and furnaces. Before this technology, the heat of an iron was controlled by unscrewing it from the overhead light socket, or unplugging the cord from the iron. Cooking was definitely a challenge, as oven heat had to be monitored with a thermometer on the oven door.

Have your students research the way a thermostat works, and then make a list of all the appliances in their home that contain thermostats.

Heat Transfer

There are three common means of heat transfer - conduction, convection and radiation.

Conduction

Have your students hold one hand on a carpet and the other on a ceramic tile. They will experience an apparent difference in temperature. This is really a difference in heat conduction. Under your supervision, have a student perform the following experiment.

Light a candle and give a paper clip to the student. Ask the student to hold the paper clip in the candle flame and describe what happens to the paper clip. The clip will become hot because heat through conduction, has transferred through actual contact from the source, (candle flame to paper clip).

A similar experiment could be performed in small groups with each group using a beaker of very hot water, and each student holding a paper clip.

Convection.

Fill a large, clear bowl 3/4 full with chilled water. (Don't chill the bowl or condensation will form on the outside). Add hot, but not boiling water to a small preserve jar fitted with a wire handle around the lip. Add enough food colouring to the hot water to make a dark solution. Swirl to mix.

Plunge the preserve jar into the bowl of chilled water, forcing it to the bottom as quickly as possible.

The coloured hot water will rise rapidly from the jar. Colder water near the surface will slowly sink. Watch the convection process in action.

Note:

Hot fluid has a lower density than the same fluid when it is cold. The hot fluid will tend to rise and spread out. As the fluid rises, it transfers some of its heat to the surrounding fluid and cools. In the bowl, the process continues until all the fluid registers the same temperature.

Radiation

Have the students stand in the Sun by a window and then in shadow. If there is no wind, you could do this experiment outside. The heat you feel while standing in the Sun is heat transferred by radiant energy. Standing close by a stove, hot plate or sun lamp will also warm you with radiant energy, when that appliance is turned on.

If your class is older, have the students research heat transfer and describe specific examples of each.

Making a Very Simple Electric Motor

Equipment:

• elastic band
• compass with a metallic case
• 2 D-cell batteries
• 2 wires with insulation removed from each end electrical tape

Wrap an elastic band around the two D cell batteries, connecting them in series (like a flashlight). Tape one wire to each end of the battery roll. Hold one end of one wire on the side of the compass case. Touch the other wire to another point on the case. The compass needle will turn. Briefly remove and retouch this wire to other points on the compass case. You should be able to find a spot on the case where you can make the compass needle spin around and around like a motor. Using electricity from the battery and the magnetism of a compass needle, you have created a simple motor.

Self and Society

Power Cut

What to do? Discuss with your students what they do when there is a power failure in the neighbourhood. How long could they go on without electricity in the summer? in the winter?

The Healthy House (Grades 9 to 11)

Have your students explore the CMHC Healthy House site on the Internet and write an essay about

• the technology of the house
• the social impact of this kind of housing
• the most amazing feature of this house

The Healthy House site

Language

Word play

Brainstorm with the students on what they think domestic technology is about. Record the ideas on flip charts or small cards, and use to build new vocabulary. This activity is also a good starting point for discussion. The Love, Leisure and Laundry Exhibit covers the technology of household chores or housework. Discuss with the class what they consider to be a definition of housework. Does it include household repairs? Gardening? Painting?

Let's Get Technical

Ask the students to bring a small gadget from home (egg beater, cookie cutters, grater, whisk, flipper, can opener, peeler, ice cream scoop). Students provide a written description of the gadget indicating its appearance, function and effectiveness.

Ad Man

Ask students to design a gadget or appliance which would perform some useful task in the home. They are to write an advertisement for this gadget, including how much it costs, what it does, where it is sold and why the consumer would want to buy it.

A Day in the Life

Students write a journal entitled "A Day in the Life" of a character from the past or the future. They incorporate this character's uses of household technology in performing their everyday chores.

The Arts

Who's the Boss?

Have the students role play the matron verses servant role in a well-to-do home of the 1890s. The matron will go through the tasks that must be accomplished that day, and the servant will complain as to why they can't be done.

Switch the time frame to 1920. A few electrical gadgets are now available, vacuum cleaner, washing machine, etc. What turn will the conversation take now that the lure of factory work offers another prospect for the maid?

The Refrigerator Guy

In the early days of refrigeration, repairmen had to come to the home to oil the working parts of the compressor, check the amount of refrigerant and ensure that it was at the correct pressure. Of course, the repairman had to be spotlessly clean. Role play an episode of a well-to-do housewife in the 1930s and her refrigerator repairman. Remember that refrigerators in the early days were quite noisy. You might want to give the students a print-out of the background information on refrigerators.

Collage

Using junk mail flyers, have the students create murals illustrating the technology of housework, or the technology of all machines used in the home.

We've Come a Long Way?

Have the sudents fold a piece of 81/2" x 11" paper in half. On one half of the paper, they draw a member of their family performing a household chore 100 years ago. On the other half of the paper, they draw a family member performing this task 100 years into the future. What are the differences? Use pastels, markers, paint or any available medium.

Math

Comparison

Using to-day's catalogues and flyers, have the students search out the prices of refrigerators, stoves, vacuum cleaners, microwaves, etc. and calculate their cost as a percentage of several monthly salaries (minimum wage clerk, secretary, teacher, lawyer). Students might search for these salaries in the newspaper employment ads.

In 1929, the price of wood stoves varied from $32.75 to $64.50. An electric stove cost from $78.25 to $99.50. If the salaries at the time were as follows:

• waitress - $30 a month
• bricklayers - $1.00 an hour
• hairdresser - $50.00 a week

- calculate the percentages of each monthly salary required to buy both types of stoves.

Prices and salaries are taken from Glazebrook, Brett, McErvel. A Shopper's View of Canada's Past. Toronto: University of Toronto Press, 1969.

Tally

Have the students count and classify all the electrical appliances in their home into categories such as: Cooking, Cleaning, Entertainment, Personal Hygiene, Laundering, etc. Graph the results. If possible, try to eliminate all the appliances that would not have been in an average home in the 1950s. Teacher input is necessary as students may not know what existed then. Graph the results. What is the difference?

Ask older students to count in their home, all the electrical appliances that have motors and those that don't. Have them graph the results.

The Price is Right

Introduce money problems concerning the electricity, gas and water bills where measurement of services and rates are involved. Show the students copies of current gas, water and electricity bills, and explain the figures to them.

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