Week 8 (Oct. 14 - 18)
Fall Break; no class Monday and Tuesday
Read: Work and Weight (Chap. 9); Kinetic and Potential Energy (Chap. 10)
PHY 202 Lecture: Electric forces, electric fields and electric potential,
Read: Work and Weight (Chap. 9); Kinetic and Potential Energy (Chap. 10)
PHY 202 Lecture: Electric forces, electric fields and electric potential,
Quiz: None.
Homework:
Joule heating/calorimetry lab. This week, you will be attempting to measure the specific heat capacity of water by observing the rate of temperature change when the water is heated using a resistive heating element. The cartridge heater we will use has a resistance of about 14 ohms. Place enough water in an insulated calorimetry cup so as to cover the cartridge heater: about 200 mL. Insert a stainless steel temperature probe into the water. Plug the temperature probe into the appropriate port of the LabPro interface. We will be using Logger Pro to measure the temperature of the water when we turn on the heater. Attach the heater to a power supply. Eventually, you will turn on the power supply to about 10 volts, and measure the electrical current—between half an amp and one amp—flowing through your cartridge heater using a multimeter. The multimeter should be set to the large (10 amp) current setting so that you don't blow the fuse!
You will collect temperature data about once per second for over half an hour. You will need about a minute of data collected prior to turning on the heater (to measure room temperature), then about 5 or 10 minutes of data while heating the water (after turning on the heater), and finally at least 30 minutes of cooling (after turning off the heater). For best results, pull the heater from the water when you turn it off so that it does not continue to heat the water. Be careful…it may be hot to the touch.
Explain your results. In particular, does your water heat at a constant rate? Why or why not? Can you determine the specific heat of water? How? You will need to use the calorimetric formula, dQ = mc dT, and also the joule-heating formula, P = I^2 R in order to determine the specific heat. Compare your measurement of the specific heat of water to that of a reputable source (cite it!). Explain any discrepancies in terms of systematic errors in your procedure, if possible. In particular, are there any heat leaks from the water as you are heating it? How might these be accounted for? And how might you make the experiment better?
Chapter 9 (3 videos):
Chapter 10 (3 videos):
Homework:
- Lever (Ex. 9.1), Hydroelectric power (Ex. 9.2),
- Work and kinetic energy (Ex. 10.1),
- Pendulum speed (Ex. 10.2),
- Work and potential energy (Ex. 10.3*)
Joule heating/calorimetry lab. This week, you will be attempting to measure the specific heat capacity of water by observing the rate of temperature change when the water is heated using a resistive heating element. The cartridge heater we will use has a resistance of about 14 ohms. Place enough water in an insulated calorimetry cup so as to cover the cartridge heater: about 200 mL. Insert a stainless steel temperature probe into the water. Plug the temperature probe into the appropriate port of the LabPro interface. We will be using Logger Pro to measure the temperature of the water when we turn on the heater. Attach the heater to a power supply. Eventually, you will turn on the power supply to about 10 volts, and measure the electrical current—between half an amp and one amp—flowing through your cartridge heater using a multimeter. The multimeter should be set to the large (10 amp) current setting so that you don't blow the fuse!
You will collect temperature data about once per second for over half an hour. You will need about a minute of data collected prior to turning on the heater (to measure room temperature), then about 5 or 10 minutes of data while heating the water (after turning on the heater), and finally at least 30 minutes of cooling (after turning off the heater). For best results, pull the heater from the water when you turn it off so that it does not continue to heat the water. Be careful…it may be hot to the touch.
Explain your results. In particular, does your water heat at a constant rate? Why or why not? Can you determine the specific heat of water? How? You will need to use the calorimetric formula, dQ = mc dT, and also the joule-heating formula, P = I^2 R in order to determine the specific heat. Compare your measurement of the specific heat of water to that of a reputable source (cite it!). Explain any discrepancies in terms of systematic errors in your procedure, if possible. In particular, are there any heat leaks from the water as you are heating it? How might these be accounted for? And how might you make the experiment better?
Chapter 9 (3 videos):
Chapter 10 (3 videos):