Refer to Multiple-Concept Example 3 to review the concepts that are needed here. A cordless electric shaver uses energy at a rate of 4.0 W from a rechargeable 1.5-V battery. Each of the charged particles that the battery delivers to the shaver carries a charge that has a magnitude of 1.6 × 10⁻¹⁹ C. A fully charged battery allows the shaver to be used for its maximum operation time, during which 3.0 × 10²² of the charged particles pass between the terminals of the battery as the shaver operates. What is the shaver’s maximum operation time?

Concept Example 3

The wattage of the headlight in Figure 19.4 is 60.0 W. Determine the number of particles, each carrying a charge of 1.60 × 10⁻¹⁹ C (the magnitude of the charge on an electron), that pass between the terminals of the 12-V car battery when the headlight burns for one hour.

Reasoning

The number of particles is the total charge that passes between the battery terminals in one hour divided by the magnitude of the charge on each particle. The total charge is the amount of charge needed to convey the energy used by the headlight in one hour. This energy is related to the wattage of the headlight, which specifies the power or rate at which energy is used, and the time the light is on.

Knowns and Unknowns The following table summarizes the data provided:

Transcribed Image Text:

Description Symbol Value Comment Wattage of headlight 60.0 W Charge magnitude per particle 1.60 x 10 19 C e Electric potential difference between battery terminals VA - VE 12 V See Figure 19.4. Time headlight is on 3600 s One hour. Unknown Variable Number of particles ?