9.2 Model of conduction in metals  (Page 5/7)

Incandescent light bulbs are being replaced with more efficient LED and CFL light bulbs. Is there any obvious evidence that incandescent light bulbs might not be that energy efficient? Is energy converted into anything but visible light?

It was stated that the motion of an electron appears nearly random when an electrical field is applied to the conductor. What makes the motion nearly random and differentiates it from the random motion of molecules in a gas?

Electric circuits are sometimes explained using a conceptual model of water flowing through a pipe. In this conceptual model, the voltage source is represented as a pump that pumps water through pipes and the pipes connect components in the circuit. Is a conceptual model of water flowing through a pipe an adequate representation of the circuit? How are electrons and wires similar to water molecules and pipes? How are they different?

An incandescent light bulb is partially evacuated. Why do you suppose that is?

An aluminum wire 1.628 mm in diameter (14-gauge) carries a current of 3.00 amps. (a) What is the absolute value of the charge density in the wire? (b) What is the drift velocity of the electrons? (c) What would be the drift velocity if the same gauge copper were used instead of aluminum? The density of copper is $8.96{\text{g/cm}}^3$ and the density of aluminum is $2.70{\text{g/cm}}^3$ . The molar mass of aluminum is 26.98 g/mol and the molar mass of copper is 63.5 g/mol. Assume each atom of metal contributes one free electron.

The current of an electron beam has a measured current of $I=50.00\mu \text{A}$ with a radius of $1.00{\text{mm}}^2$ . What is the magnitude of the current density of the beam?

A high-energy proton accelerator produces a proton beam with a radius of $r=0.90\text{mm}$ . The beam current is $I=9.00\mu \text{A}$ and is constant. The charge density of the beam is $n=6.00\times {10}^{11}$ protons per cubic meter. (a) What is the current density of the beam? (b) What is the drift velocity of the beam? (c) How much time does it take for $1.00\times {10}^{10}$ protons to be emitted by the accelerator?

Consider a wire of a circular cross-section with a radius of $R=3.00\text{mm}$ . The magnitude of the current density is modeled as $J=c{r}^2=5.00\times {10}^6\frac{\text{A}}{{\text{m}}^4}{r}^2$ . What is the current through the inner section of the wire from the center to $r=0.5R$ ?

The current of an electron beam has a measured current of $I=50.00\mu \text{A}$ with a radius of $1.00{\text{mm}}^2$ . What is the magnitude of the current density of the beam?

The current supplied to an air conditioner unit is 4.00 amps. The air conditioner is wired using a 10-gauge (diameter 2.588 mm) wire. The charge density is $n=8.48\times {10}^{28}\frac{\text{electrons}}{{\text{m}}^3}$ . Find the magnitude of (a) current density and (b) the drift velocity.