Book cover for Physics

Physics

John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler

ISBN #9781118486894

10th Edition

2,562 Questions

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Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This section covers the fundamentals of electric potential energy and electric potential, emphasizing that electric potential is energy per unit charge and that only differences in potential (voltage) are measurable. It explains how work done by electric forces relates to changes in potential energy, details the concept and properties of equipotential surfaces, and explores capacitors along with the role of dielectrics in enhancing capacitance. Real-world applications in biomedical diagnostics and everyday electronic devices demonstrate the practical importance of these concepts.

Learning Objectives

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Key Concepts

CONCEPT

DEFINITION

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Example Problems

Example 1

During a particular thunderstorm, the electric potential difference between a cloud and the ground is $V_{\text {cloud }}-V_{\text {ground }}=1.3 \times 10^{8} \mathrm{V},$ with the cloud being at the higher potential. What is the change in an electron's electric potential energy when the electron moves from the ground to the cloud?

Example 2

A particle with a charge of $-1.5 \mu \mathrm{C}$ and a mass of $2.5 \times 10^{-6} \mathrm{kg}$ is released from rest at point $A$ and accelerates toward point $B$, arriving there with a speed of $42 \mathrm{m} / \mathrm{s}$. The only force acting on the particle is the electric force. (a) Which point is at the higher potential? Give your reasoning. (b) What is the potential difference $V_{\mathrm{B}}-V_{\mathrm{A}}$ between $\mathrm{A}$ and $\mathrm{B} ?$

Example 3

Suppose that the electric potential outside a living cell is higher than that inside the cell by 0.070 V. How much work is done by the electric force when a sodium ion (charge $=+e$ ) moves from the outside to the inside?

Example 4

A particle has a charge of $+1.5 \mu \mathrm{C}$ and moves from point $A$ topoint $B$, a distance of $0.20 \mathrm{m}$. The particle experiences a constant electric force, and its motion is along the line of action of the force. The difference between the particle's electric potential energy at $A$ and at $B$ is $E P E_{A}-$ $\mathrm{EPE}_{B}=+9.0 \times 10^{-4} \mathrm{J} .$ (a) Find the magnitude and direction of the electric force that acts on the particle. (b) Find the magnitude and direction of the electric field that the particle experiences.

Example 5

Multiple-Concept Example 3 employs some of the concepts thatare needed here. An electric car accelerates for $7.0 \mathrm{s}$ by drawing energy from its $290-\mathrm{V}$ battery pack. During this time, $1200 \mathrm{C}$ of charge passes through the battery pack. Find the minimum horsepower rating of the car.

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Step-by-Step Explanations

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Common Mistakes

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