Skip to Content Go to sign in Skip to Primary Navigation Skip to Secondary Navigation Skip to Page Navigation Skip to Header Navigation Skip to Footer Navigation Read more about accessability options and our navigation

Physics Classroom is making strides to make our site accessible to everyone. Our site contains 6 navigation areas. The Primary, Secondary, and Page Level navigations have a screen reader version of their nav structure that allows using the left and right keys to navigate sibling navigation items, and up or down keys to navigate parent or child navigation items. The others can be navigated using tabs. The Primary Navigation handles the first 2 levels of site pages. The Secondary (which is not always available) handles the 3rd and 4th level of structure. The Page level navigation allows you to navigate the current page's headings quickly. The Header Navigation contains the Light/Dark Mode toggle, Search, Notifications and account login. The Breadcrumb Navigation contains the breadcrumb of the current page. If the current page has a breadcrumb, you can get to it by skipping to the content and tabbing in reverse (shift plus tab). The Footer Navigation contains links such as Privacy, Contact, about and terms. Some resources contain an Audio Player that can be activated by holding down the T key for 3 seconds, and then using K to pause and resume. While not every area of Physics Classroom is usable purely from keyboard and screen reader, we are committed to continue work on making this possible. If you have questions or need additional help, please use this link to contact us.

Return to screen reader navigation
Home Minds On Electric Circuits Mission EC6 P, V, I, R, and Cost Calculations Help Help 7

Mission EC6 P, V, I, R, and Cost Calculations

The Question

A 40-Watt light bulb plugged into a 120-Volt outlet is left on for 60 seconds. How much energy (in Joules) is used up by the bulb during this time?
 
(Note: The numbers in this problem are randomly selected and may differ from those above.)

Define Help

Mathematically, power is a rate quantity - a time-based quantity. It is the rate at which an appliance transforms electrical energy into other forms of energy. The power (P in Watts) of a light bulb is related to the energy transformed by the bulb (∆E in Joules) and the time (t in seconds) that the bulb is used. These quantities are related by the equation
P = ∆E / t.

Don't be Fooled

An introductory Physics course will typically include a lot of algebraic problem-solving. Students quickly gain an impression that every numerical value provided within a problem must be used. But don't be fooled! Physics should involve an understanding of physical concepts and not simply plug-and-chug exercises. In Physics, we attempt to answer questions about the physical world. In answering such questions, we must discriminate between information that is pertinent and information that is impertinent to the solution. The ability to make decisions about the pertinence of such information comes from a solid grasp of concepts and definitions. In this problem, such discrimination allows a student to recognize that the voltage is not important to the solution of the problem.

Hot Link