College Physics

Example 20.1 Calculating Currents: Current in a Truck Battery and a Handheld Calculator (a) What is the current involved when a ...

by electrons—that is, negative charges move. In ionic solutions, such as salt water, both positive and negative charges move. Th ...

crowd of people with movement in different directions but a general trend to move forward. There are lots of collisions with ato ...

We can obtain an expression for the relationship between current and drift velocity by considering the number of free charges in ...

RearrangingI=nqAvdto isolate drift velocity gives v (20.11) d= I nqA = 20.0 A (8.342×10^28 /m^3 )(–1.60×10–19C)(3.310×10–6m^2 ) ...

Example 20.4 Calculating Resistance: An Automobile Headlight What is the resistance of an automobile headlight through which 2.5 ...

20.3 Resistance and Resistivity Material and Shape Dependence of Resistance The resistance of an object depends on its shape and ...

Table 20.1Resistivitiesρof Various materials at20ºC Material Resistivityρ( Ω⋅m) Conductors Silver 1. 59 ×10−^8 Copper 1.72×10−8 ...

Example 20.5 Calculating Resistor Diameter: A Headlight Filament A car headlight filament is made of tungsten and has a cold res ...

Figure 20.12The resistance of a sample of mercury is zero at very low temperatures—it is a superconductor up to about 4.2 K. Abo ...

is the temperature dependence of the resistance of an object, whereR 0 is the original resistance andRis the resistance after a ...

Figure 20.15(a) Which of these lightbulbs, the 25-W bulb (upper left) or the 60-W bulb (upper right), has the higher resistance? ...

For the hot headlight, we know voltage and current, so we can useP=IV to find the power. For the cold headlight, we know the vol ...

Solution for (a) The energy used in kilowatt-hours is found by entering the power and time into the expression for energy: E=Pt= ...

Figure 20.17The potential differenceVbetween the terminals of an AC voltage source fluctuates as shown. The mathematical express ...

(20.41) Irms= I 0 2 and (20.42) Vrms= V 0 2 . where rms stands for root mean square, a particular kind of average. In general, t ...

Why Use AC for Power Distribution? Most large power-distribution systems are AC. Moreover, the power is transmitted at much high ...

PhET Explorations: Generator Generate electricity with a bar magnet! Discover the physics behind the phenomena by exploring magn ...

Figure 20.22(a) A fuse has a metal strip with a low melting point that, when overheated by an excessive current, permanently bre ...

Figure 20.24An electric current can cause muscular contractions with varying effects. (a) The victim is “thrown” backward by inv ...