work, energy & power. work a measure of the amount of energy transformed from one form to...
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WORK, ENERGY & POWER
Work
A measure of the amount of energy transformed from one form to another
For example, work is done when energy is used to move something or produce heat or light
Units: Joules (J)
Energy
Energy is the ability to do work
Units: Joules (J)
Potential Energy
Stored energy
Examples: Gravitational Elastic chemical
Kinetic Energy
Energy of objects in motion Heat and light are forms of kinetic
energy
Electrical Energy
Electrical energy can be transformed into many other kinds of energy
Examples: heat, light, sound, mechanical energy
Power
The rate at which work is done (more work in less time = more power)
Units: Watts (W) or kilowatts (kW)
Formulas
P = power (W) E = Energy (J) T = time (s) V = volts (V) I = current (A)
€
P =VI
€
P = Et
Sample Problems p. 340
1. P =
P =
= 686 W€
Et
€
24000J35s
2.
E = Pt= 45 W x (28 x 60)s= 75 600 J
€
4.P = VI = 0.42 V x 1.8 A = 0.76 W
5. V =
=
= 14.2 V€
PI
€
37W2.6A
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