Insulators are materials that reduce heat flow. Nature uses many types of insulation to protect animals from losing too much hea
t. Blubber, feathers, and hair all help animals retain body heat. Animals often insulate their homes with wood chips, grass, and even shredded newspaper and bits of cloth. Humans have also had to find ways of insulating ourselves from the cold. In past times, homes were constructed with thick walls to protect against heat loss. Today, materials such as fiberglass and foam are often incorporated into walls and floors for insulation. In this activity, you will compare the heat-retaining ability of several insulators.
OBJECTIVES
Build and use a calorimeter to measure rate of heat loss.
Analyze data using comparative graphs.
In this experiment, you will be using a “coffee cup” calorimeter to measure the rate of heat loss for several substances and determining which of the substances is the best insulator. You will be testing the insulating capabilities of three types of fabric and the control will be air. The three types of fabric are:
Test Sample 1: 52% cotton/48% poly fabric
Test Sample 2: 100% acrylic fabric
Test Sample 3: 80% cotton/20% poly fabric
For the control, and each test sample, you will be measuring the amount of heat lost by the water in the calorimeter over 6 minutes, taking the temperature every 30 seconds. Be sure to record your data on your data sheet . View the animation to complete this experiment.
Answering the following questions will help you to focus on the outcomes of these experiments: Construct a graph of temperature versus time. Put temperature on the y-axis and time on the x-axis. Graph all three sets of data on the same graph. Use a different colored pencil for each test material. Provide a key on the graph relating the pencil color to the test material. Calculate the change in temperature from start to finish for the air and each of the samples and record on your data sheet. Which water sample lost the least amount of heat energy over the 6-minute time interval? Was the rate of heat loss constant during each experiment? How can you tell? Which material was the best insulator? Which material was the least effective insulator? Write a summary paragraph discussing this experiment and the results. Use the following questions and topics to help guide the content of your paragraph. According to your data, was your hypothesis correct? (Be sure to refer to your data and graphs when answering this question.) Summarize the conclusions that you can draw from this experiment. Use the questions above to guide your ideas. Summarize any difficulties or problems you had in performing the experiment that might have affected the results. Describe how you might change the procedure to avoid these problems. Explain why the design of the bird's nest in the picture provides good insulation for the eggs. Submit your data sheet, graph, and answers to all of the questions in the essay box below.
OBJECTIVES
Build and use a calorimeter to measure rate of heat loss.
Analyze data using comparative graphs.
In this experiment, you will be using a “coffee cup” calorimeter to measure the rate of heat loss for several substances and determining which of the substances is the best insulator. You will be testing the insulating capabilities of three types of fabric and the control will be air. The three types of fabric are:
Test Sample 1: 52% cotton/48% poly fabric
Test Sample 2: 100% acrylic fabric
Test Sample 3: 80% cotton/20% poly fabric
For the control, and each test sample, you will be measuring the amount of heat lost by the water in the calorimeter over 6 minutes, taking the temperature every 30 seconds. Be sure to record your data on your data sheet . View the animation to complete this experiment.
Answering the following questions will help you to focus on the outcomes of these experiments: Construct a graph of temperature versus time. Put temperature on the y-axis and time on the x-axis. Graph all three sets of data on the same graph. Use a different colored pencil for each test material. Provide a key on the graph relating the pencil color to the test material. Calculate the change in temperature from start to finish for the air and each of the samples and record on your data sheet. Which water sample lost the least amount of heat energy over the 6-minute time interval? Was the rate of heat loss constant during each experiment? How can you tell? Which material was the best insulator? Which material was the least effective insulator? Write a summary paragraph discussing this experiment and the results. Use the following questions and topics to help guide the content of your paragraph. According to your data, was your hypothesis correct? (Be sure to refer to your data and graphs when answering this question.) Summarize the conclusions that you can draw from this experiment. Use the questions above to guide your ideas. Summarize any difficulties or problems you had in performing the experiment that might have affected the results. Describe how you might change the procedure to avoid these problems. Explain why the design of the bird's nest in the picture provides good insulation for the eggs. Submit your data sheet, graph, and answers to all of the questions in the essay box below.
1 answer:
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Answer:
1. The current will drop to half of its original value.
Explanation:
The problem can be solved by using Ohm's law:
where
V is the voltage across the circuit
R is the resistance of the circuit
I is the current
We can rewrite it as
In this problem, we have:
- the resistance of the circuit remains the same: R' = R
- the voltage is decreased to half of its original value:
So, the new current will be
so, the current will drop to half of its original value.