(III) The filament of a lightbulb has a resistance of 12 Ω at 20°C and 140 Ω when hot (as in Problem 19). ( a ) Calculate the temperature of the filament when it is hot, and take into account the change in length and area of the filament due to thermal expansion (assume tungsten for which the thermal expansion coefficient is ≈ 5.5 × 10 −6 C° −1 ). ( b ) In this temperature range, what is the percentage change in resistance due to thermal expansion, and what is the percentage change in resistance due solely to the change in ρ ? Use Eq. 25–5.
(III) The filament of a lightbulb has a resistance of 12 Ω at 20°C and 140 Ω when hot (as in Problem 19). ( a ) Calculate the temperature of the filament when it is hot, and take into account the change in length and area of the filament due to thermal expansion (assume tungsten for which the thermal expansion coefficient is ≈ 5.5 × 10 −6 C° −1 ). ( b ) In this temperature range, what is the percentage change in resistance due to thermal expansion, and what is the percentage change in resistance due solely to the change in ρ ? Use Eq. 25–5.
(III) The filament of a lightbulb has a resistance of 12 Ω at 20°C and 140 Ω when hot (as in Problem 19). (a) Calculate the temperature of the filament when it is hot, and take into account the change in length and area of the filament due to thermal expansion (assume tungsten for which the thermal expansion coefficient is ≈ 5.5 × 10−6 C°−1). (b) In this temperature range, what is the percentage change in resistance due to thermal expansion, and what is the percentage change in resistance due solely to the change in ρ? Use Eq. 25–5.
(b) Consider a particular phone that has a battery rated at 2.500 mAh. The battery operates at a potential difference of 3.90 V. How much energy, in units of kilowatt-hours, is stored in
a fully charged battery?
0.975-2
✓kWh
(c) If electricity costs $0.16 (or 16.0 cents) per kilowatt-hour, what is the value of the total amount of energy stored in this battery? Express your answer in cents (or 0.01 of a dollar).
How can you relate the energy from part (b) to the cost per kilowatt-hour to find the total cost?
(d) When the phone is idle (that is, turned on but not making calls or texts, using GPS, or running any power-hungry apps), it will operate continuously for 32.2 hours from a fully
charged battery, until the battery runs out. How much average current does the phone draw while idle? Express your answer in milliamperes,
MA
(b)
Consider a particular phone that has a battery rated at 4,000 mAh. The battery operates at a potential difference of 3.90 V. How much energy, in units of kilowatt-hours, is stored in a fully charged battery?
kWh
(c)
If electricity costs $0.12 (or 12.0 cents) per kilowatt-hour, what is the value of the total amount of energy stored in this battery? Express your answer in cents (or 0.01 of a dollar).
¢
(d)
When the phone is idle (that is, turned on but not making calls or texts, using GPS, or running any power-hungry apps), it will operate continuously for 29.2 hours from a fully charged battery, until the battery runs out. How much average current does the phone draw while idle? Express your answer in milliamperes.
mA
The circuit shown below can be used to measure the resistance of a platinum resistance thermometer (PRT). AB is a uniform resistance wire of length 1.00 m and C is a sliding contact on this wire. A standard resistor R is included in the circuit. The position of C is adjusted until the voltmeter V reads zero.
(ii) The PRT consists of 9.00 m of wire of diameter 8.4 × 10-2 mm. The voltmeter reads 0 V when l1 = 0.422 m. If the standard resistor, R, has a resistance of 220 Ω, what is the resistivity of platinum? Show that you have checked that the value for the resistivity and its unit are sensible.
Chapter 25 Solutions
Physics for Scientists and Engineers with Modern Physics
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How To Solve Any Resistors In Series and Parallel Combination Circuit Problems in Physics; Author: The Organic Chemistry Tutor;https://www.youtube.com/watch?v=eFlJy0cPbsY;License: Standard YouTube License, CC-BY