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Ohm’s Law Practice Worksheet With Answers
23 questions By Tony R. Kuphaldt
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Question 1 of 23
Define the following terms: energy, work, and power.
Reveal answerWork is the exertion of a force over a distance. Energy is the capacity to perform work. Power is the rate of work performed per unit time.
Notes:Students may find a basic physics text helpful in obtaining these definitions. “Work” is a difficult concept to precisely define, especially for students unfamiliar with basic physics. Technically, it is the vector dot-product of force and displacement, meaning that work equals force times distance only if the force and distance vectors are precisely parallel to each other. In other words, if I carry a 10 kg mass (lifting up against the tug of gravity) while walking parallel to the ground (not going up or down), the force and displacement vectors are perpendicular to each other, and the work I do in carrying the mass is zero. It is only if my force is directed precisely the same direction as my motion that all of my effort is translated into work.
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Question 2 of 23
Voltage is commonly defined as “electrical pressure.” The unit of the volt, however, may be defined in terms of more fundamental physical units. What are these units, and how do they relate to the unit of the volt?
Reveal answer1 volt is equal to 1 joule of energy imparted to 1 coulomb of charge (6.25 ×1018 electrons):
$$V= \frac {W}{Q}$$
Where,
V = Voltage (volts)
W = Work, or potential energy (joules)
Q = Charge (coulombs)
Notes:Note that I use the letter “V” to denote voltage rather than “E” as I usually do. This is because in general physics work, “E” usually stands for either “Energy” or “Electric field”. Some electronics reference books use the letter “E” for voltage, while others use the letter “V”, or even use the two letters interchangeably.
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Question 3 of 23
Electric current is measured in the unit of the ampere, or amp. What is the physical definition for this unit? What fundamental quantities constitute 1 ampere of electric current?
Reveal answer1 ampere of electric current is the rate of electron motion equal to 1 coulomb per second:
$$I= \frac {Q}{t}$$
Where,
I = Electric current (amperes)
Q = Charge in motion (coulombs)
t = Time (seconds)
Notes:It may be helpful at this point to review the number of electrons constituting one coulomb of charge: 6.25 ×1018 electrons.
Technically, current’s mathematical definition involves calculus:
$$I= \frac {dQ}{dt}$$
However, students at this stage may not be ready to explore derivatives yet, and so the equation give in the answer for (average) current will suffice.
The questions are very interesting.