Fermi National Accelerator Laboratory is the premiere high energy physics laboratory in the United States. Typical experiments at Fermilab involve producing beams of subatomic particles, accelerating them to high velocities, and them smashing them into stationary targets or other particle beams. Read the following passage from their newsletter,.
[Physicist Sergei] Nagaitsev's group has created a record-breaking electron beam with a continuous current of 500 milliamps at an energy of 3.5 MeV. To the layperson, these numbers may not seem significant. After all, half an amp is the current flowing through the wire of a typical light bulb. However, the electrons in the beam travel at a much higher energy than those in a wire, leading to a beam power that even amazes the non-experts. "We are holding a world record in DC beam power," Nagaitsev said. "About two megawatts." For comparison, this amount of power is sufficient to operate two thousand kitchen refrigerators simultaneously.
Verify the claims of the author through the following set of calculations…
What kind of typical light bulb would have a half an amp of current running through it? (Assume a North American household voltage of 120 V.)
Does the beam described by Nagaitsev actually have a power of about two megawatts? Justify your answer with a calculation.
What power does Nagaitsev assume a typical home refrigerator needs to operate? Justify your answer with a calculation.
What make and model of household refrigerator would require the approximate power you calculated in part c.?
Purchase the refrigerator you identified in part d.
Which of these apparently similar rechargeable batteries is "better"? Answer this by computing the…
charge in…
milliamp hours [mAh]
coulombs [C]
potential energy in…
milliwatt hours [mWh]
joues [J]
Compile your findings in a table like this one.
Two apparently similar rechargeable batteries
type
voltage
charge
energy
(V)
(mAh)
(C)
(mWh)
(J)
NiZn
1.6
2,500
NiMH
1.2
2,500
homework
Read the following description of the execution of Kenneth Stewart in Virginia on 23 September 1998.
The electric cycle, 1,825 volts at approximately 7.5 amps for 30 seconds, then 240 volts at approximately 1.5 amps for 60 seconds… a 5 second pause intervenes, and the cycle is repeated, was designed to render the condemned brain dead within the first few moments. The function of the remainder of the cycle is to stop the body's organs so that a physician can certify that death has occurred….
Determine the total electric energy delivered to Mr. Stewart on the day of his execution.
The useful life of a battery is stated in ampere-hours. A typical 12 V car battery has a discharge time of 60 Ah. Suppose you left the headlights on when your car was parked and that they drew 3 A of current.
How long would your battery last before it went dead?
How much energy would it consume?
A standard 60 W 120 V light bulb has a tungsten filament that is 53.3 cm long and 46 μm in diameter.
What is the light bulb's operating resistance?
Determine the cross sectional area of the filament.
Calculate the resistivity of tungsten using the results of part a. and b.
How does the resistivity calculated above compare to the value quoted in standard reference tables? Why are these two values so different?
How can a 53.3 cm filament fit into a light bulb that is only a few centimeters wide?
