Work in Electrical Systems

Notes 2.3

Forces are applied to charged objects by electric fields—electric fields are created by other charges. You can’t see or hear electrical work, you can only see the results of the work because it is converted into other forms of energy such as rotation, light, sound, and heat.

I. CoulombsA. 1 electron = 1.6 x 10-19 CB. 1 C = charge of 6.25 x 1018 electronsC. the net charge of 1 coulomb = 6.25 billion billion

electrons on the bottom plate of a capacitor rather than on the top plate.

II. Work in Electrical SystemsA. E = FE/q (electric field equals force divided by charge)B. When a charge is moved in an electric field, work is done.C. ΔV = E x d (change in voltage equals electric field times distance moved)

D. W = ΔV x q (Work equals change in voltage times charge)—electrical work is the product of potential difference and charge moved.E. 1V = 1 J/C ( One Volt = 1 Joule per Coulomb)F. vectors point away from the positive charge and toward the negative charge—work can be positive or negative

III. Electric Charge and CurrentA. 1A = 1C/s ( One Ampere equals one Coulomb per second)B. I = q/Δt (Current equals charge divided by change in time)C. 1C = 1 A∙s (1 Coulomb equals 1 ampere∙second)D. 1 ampere∙hour = 3600 coulombs

IV. Effects of Electrical WorkA. movementB. thermal energyC. lightD. sound

V. Efficiency of Electrical DevicesA. E = ow/iwB. Not all electrical work is converted into mechanical work; therefore, no electrical device can ever be 100% efficient.

VI. Why Use Electricity to Do Work?A. Produced by:1. burning coal, gas, or oil to produce thermal energy2. thermal energy converts water into high-pressure steam3. steam pressure is used to drive turbines4. turbines drive electrical generators to produce electricity

B. Reasons for using electricity:1. affordable2. can move over long distances

through overhead or underground wires3. can be transformed into other

forms of energy and work4. convenient and easy to use