Download Chapter 18 worksheet AP physics

Chapter 18 worksheet AP physics
Define the following:
Source of emf
Emf
Electric current
Electron current
Electrical resistance
Ohm’s law
Electric power
Direct current
Alternating current
Root mean square current
Electric generator
sinusoidal
Write the equations for the following and state their units and any conversion
Electric current
Electric resistance
Ohm’s law
Electric power in a dc circuit
Alternating current electricity
Questions
1. What is an electric battery?
2. Describe the construction of an electric battery.
3. Explain electromotive force.
4. When does an electric current exist?
5. What is conventional current and how does it flow?
6. Describe resistivity.
7. What is ρ?
8. What is ξ?
9. Explain the relationship of work to power in electricity.
10. Compare and contrast dc and ac current.
Text questions: # 1, 5, 121 pg. 579-580
Problems:
1. The starter motor on a particular car draws a current of 50 amperes through a copper
cable. Determine the number of
a. coulombs of charge which pass a particular point in the cable in 15 s.
b. and electrons which pass a particular point in the wire in 15 seconds.
2. a. Determine the electrical resistance of a 20.0 m length of tungsten wire of radius
0.200 mm. B.. If the temperature of the wire does not change, determine thee resistance
of the same wire if it is stretched to a length of 60.0 m. The resistivity of tungsten is
5.60 x 10 -8 Ωm.
3. The resistance of the tungsten wire in the previous problem is 80.0 Ω at 0.0 C .
Determine the resistance of the same wire if the temperature is raised to 50.0 C. b. The
resistance of a carbon wire is 80.0 Ω at 0.0 C, Determine the resistance of the wire at 50.0
C. Explain why the resistance of each substance changes as it does with the increasing
temperature. Note: the temperature coefficient of resistance is 0.0045 per degree Celsius
for tungsten and –0.00050 per degree Celsius for carbon.
4. It is estimated that the typical American child watches 31 hours of television per
week. If the average television draws 1.00 ampere of current from a 120 volt line,
determine the
a. power rating of the television in watts,
b.. number of kilowatt-hours of electrical energy consumed in one year during the time
that the child watches the TV and
c. yearly cost to the parent if electricity costs 8.00 cents per kilowatt-hour.
5. An electric immersion heater rated at 250 watts is inserted in a 100 gram aluminum
cup which contains 200 grams of water. The initial temperature of the cup and water is
20 C. Determine the time required for the temperature of the cup + water to rise to 90 C
Note: the specific heat of aluminum is .220 cal/gC and that for water is 1.00 cal/gC.
6.
a.
b.
c.
d.
A 10.0 Ω resistor is connected to a 120 volt ac line. Determine the
average power dissipated in the resistor
rms current through the resistor
maximum instantaneous current through the resistor
maximum instantaneous power dissipated in the resistor.
7. Draw all the symbols used in drawing electrical schematics.