Chapters 33-34

Chapters 33-34

1. 33.1

   • an electric field is a storehouse of energy
   • The space around a concentration of electric charge is different from how it would be if the charge were not there. If you walk by the charged dome of an electrostatic machine—a Van de Graaff generator, for example— you can sense the charge. Hair on your body stands out—just a tiny bit if you’re more than a meter away, and more if you’re closer. The space is said to contain an electric field.
   • force fields can attract or repeal things within it
   • if you drop a ball from building on earth the gravitational pull will make it accelerate down. The gravitational pull on earth can also be referred to as a force field or a gravitational field
   • An electric field is what we call the force field that surrounds electric charges.

2. 33.4

   • when we move charge in an exhausting electrical field their is work being done
   • A charged particle in an electrical field has potential energy.
   • Work is done when a force moves something in the direction of the force.
   • An object has potential energy by virtue of its location– say, where it is in a force field. For example, doing work by lifting an object increases its gravitational potential energy.
   • electrical potential energy occurs in environments when you have multiple electrical charges and what that means is that you have to do work to move the charges in the exhausting electric field which gives them electrical potential energy
   • electricity=electrons

3. 33.5

   • Electric potential is not the same as electrical potential energy. Electric potential is electrical potential energy per charge.
   • EPE/Charge= EP
   • when there is greater electric potential energy then their is more electric potential
   • amount of electric potential energy per unit of charge electric potential is measured in volt (V)
   • when there is greater electric potential energy then their is more electric potential
   • Voltage produces a flow of charge, or current, within a conductor.
   • The flow is restrained by the resistance it encounters.
   • Ohms Law
     • the first half of ohms law states that current and voltage are directly proportional
     • the second half of ohms law is that current and resistance and inversely proportional
   • the amount of electrical potential energy is dependent on the voltage of the thing
   • electric potential is measured in volt (V)
   • The rate at which energy is transferred by electric current is power.

4. 34.2

   • electric current is the flow of electric charge electric current is m easured in amperes (A)
   • 1 ampere= 1 coulomb of charge per second (1 amp= 1 coulomb/1 second)
   • ampere is the rate at which charge flows

5. 34.3-34.4

   • The electric fields of voltage sources such as batteries and generators supply energy that allows charges to move steadily.
   • Power utilities use electric generators to provide the 120 volts delivered to home outlets.
   • This means that 120 joules of energy is supplied to each coulomb of charge that is made to flow in the circuit.
   • The amount of charge that flows in a circuit depends on the voltage provided by the voltage source.
   • The current also depends on the resistance that the conductor offers to the flow of charge—the electric resistance.

6. 34.5

   • The resistance of a wire depends on the conductivity of the material in the wire and on the thickness and length of the wire.
   • Thick wires have less resistance than thin wires. Longer wires have more resistance than short wires.
   • current= voltage/resistance (CRV) 1 ampere = 1 volt o ver /ohm
   • The relationship among voltage, current, and resistance is called Ohm’s law
   • if a voltage of 12 volts us impressed across the same circuit the current will be 12 amperes Ohms law should remind me of Newton's second law ( A= F/M)
   • A low resistance permits larger current which nattily produces more heat a short circuit is when you have to much current if you made a circuit with no resistance it would short circuit

7. 34.6

   • Your body’s resistance ranges from about 100 ohms if soaked with salt water to about 500,000 ohms if your skin is very dry.
   • Touch the electrodes of a battery with dry fingers and your resistance to the flow of charge would be about 100,000 ohms.
   • handling appliances with wet hands can be dangerous
   • If you touch surfaces of different potentials, you become a pathway for current.

8. 34.11

   • Electric power is equal to the product of current and voltage. electric power = current × voltage
   • If the voltage is expressed in volts and the current in amperes, then the power is expressed in watts. 1 watt = (1 ampere) × (1 volt)
   • The power and voltage on the light bulb read “60 W 120 V.” The current that would flow through the bulb is:
I = P/V = (60 W)/(120 V) = 0.5 A.