4. Energy Resources & Energy Transfers

• increasing the impact time of an object decreases the force acting on it without changing the momentum
• chemical energy is energy stored in chemical substances and which can be released in chemical reaction
• a commutator is a device used to allow current to flow to and from the coil of a d.c motor or generator
• conduction is the transfer of heat energy or electrical energy through a material without the material itself moving
• a conductor is a substance that transmits heat or allows an electric current to pass through it
• convection is the transfer of heat through a material by movement of the material itself
• efficiency is the fraction of energy that is converted into useful energy
• when transmitting electricity, energy is lost because the current heats the wires. the higher the current, the more the wires are heated and the greater the amount of energy lost as heat
• power is the rate of energy