Physics
Week #7 Chapter 10 Static and Current Electricity
Exercises
(p.221)
6. Strictly speaking, will a penny be slightly more massive if it has a negative charge or a positive charge? Explain.
A negative charge because when it is negatively charged electrons are added to the penny.
17. What is the voltage at the location of a 0.0001 C charge that has an electric potential energy of 0.5 J (both voltage and potential relative to the same reference point)?
Potential = energy
Charge = 0.5 J / 0.0001 C = 5,000 V
20. Is it correct to say that energy from a car battery ultimately comes from fuel in the gas tank? Defend your answer.
It would be correct to say that energy from a car battery comes from fuel in the gas tank and vice versa; without neither the car would not have any energy to move.
Problems
(p.223)
8. The wattage marked on a light bulb is not an inherent property of the bulb; rather, it depends on the voltage to which it is connected, usually 110 or 120 V. Show that the current in a 60-W bulb connected in a 120-V circuit is 0.5 A.
P = I * V, I = P / V
(60W) / (120V) = 0.5 A
10. Using the formula Power = current X voltage, show that the current drawn by a 1200-W hair dryer connected to 120 V is 10 A. Then using your same method for the solution to the previous problem, show that the resistance of the hair dryer is 12 Ω.
Resistance = Voltage / Current
1200 W / 120 V = 10 A
120 V / 10 A = 12 Ω
Chapter 11 Magnetism and Electromagnet Induction
Exercises
(p.242)
16. When steel naval ships are built, the location of the ship-yard and the orientation in the ship while in the ship-yard are recorded on a brass plaque permanently fixed to the ship. Why?
Brass doesn’t erode and it doesn’t polarize. Next the reason it is recorded on a metal plaque is to show record of where the boat was manufactured and to give a changeless frame number and year it was constructed or dispatched.
34. Your friend says that, if you crank the shaft of a DC motor
Exercises
(p.221)
6. Strictly speaking, will a penny be slightly more massive if it has a negative charge or a positive charge? Explain.
A negative charge because when it is negatively charged electrons are added to the penny.
17. What is the voltage at the location of a 0.0001 C charge that has an electric potential energy of 0.5 J (both voltage and potential relative to the same reference point)?
Potential = energy
Charge = 0.5 J / 0.0001 C = 5,000 V
20. Is it correct to say that energy from a car battery ultimately comes from fuel in the gas tank? Defend your answer.
It would be correct to say that energy from a car battery comes from fuel in the gas tank and vice versa; without neither the car would not have any energy to move.
Problems
(p.223)
8. The wattage marked on a light bulb is not an inherent property of the bulb; rather, it depends on the voltage to which it is connected, usually 110 or 120 V. Show that the current in a 60-W bulb connected in a 120-V circuit is 0.5 A.
P = I * V, I = P / V
(60W) / (120V) = 0.5 A
10. Using the formula Power = current X voltage, show that the current drawn by a 1200-W hair dryer connected to 120 V is 10 A. Then using your same method for the solution to the previous problem, show that the resistance of the hair dryer is 12 Ω.
Resistance = Voltage / Current
1200 W / 120 V = 10 A
120 V / 10 A = 12 Ω
Chapter 11 Magnetism and Electromagnet Induction
Exercises
(p.242)
16. When steel naval ships are built, the location of the ship-yard and the orientation in the ship while in the ship-yard are recorded on a brass plaque permanently fixed to the ship. Why?
Brass doesn’t erode and it doesn’t polarize. Next the reason it is recorded on a metal plaque is to show record of where the boat was manufactured and to give a changeless frame number and year it was constructed or dispatched.
34. Your friend says that, if you crank the shaft of a DC motor