Shared Flashcard Set

Details

Electric Potential--Exam 2
electric potential energy, capacitors, conductors
23
Physics
03/01/2011

Term
 Define Electric Potential Energy (U)
Definition
 EPE=qEd, these are conservative forces   energy charge has in an electric field
Term
 Define Electric Potential (V)
Definition
 EP=EPE/q, this is the position in electric field (no charge needs to be present)
Term
 Define Capacitance (C)
Definition
 C=Q/V, a measure of the amount of electrical energy stored (or separated) for a given electric potential.
Term
 Define Dielectric
Definition
 An electrical insulator that can be polarized by an applied electric field
Term
 Describe the physics of capacitors in parallel and series
Definition
 In parallel, cap's add like r's in series (Ceq=C1+C2...) In series, cap's add like r's in parallel (Ceq=C1C2/C1+C2 OR 1/Ceq=1/C1+1/C2...)
Term
 How are electric field and electric potential related mathematically?
Definition
 EP=Ed=EPE/q=V--> V=kq/r---->E=kq/r^2*Electric field lines are perpindicular to V lines
Term
 Discuss the physics of a wire connected to a battery.
Definition
 Electrons move down a wire just like water moves down a pipe--in case of water, GPE is greater at one side, so it moves down in the pipe in the direction away from the high PEIn the case of the wire, EPE must also be higher at one side, so electrons travel away from the higher PE (one side of the battery is some amount of V and the other is 0V)
Term
 Electric potential of a point charge
Definition
 V=kq/r
Term
 Electric potential of an electric field
Definition
 constant-- abs(E)= ∆V/∆X   or ∆V=-E∆X
Term
 How much work is required to assemble two protons 1cm apart?
Definition
 U=qVU=q2V1U=q2(kq1/r12)U=kq1q2/r12*Just need q for a proton*
Term
 Capacitance of a parallel plate capacitor
Definition
 C=єoA/d єo=8.85X10^-12 A=m^2 d=m A=(pi)r^2
Term
 How much energy is stored in a capacitor?
Definition
 U=1/2CV^2 must be conncected to a battery, and energy stored is used in short, quick bursts
Term
 Uses of capacitors
Definition
 Intermittent windshield wipers, flash bulb camera, timing circuits, tune frequent radios, filters in power supplies
Term
 What do capacitors do in circuits?
Definition
 In circuits, cap's charge up and provide delay time because of quick bursts of energy. When a circuit is switched off cap's slowly discharge
Term
 What do resistors do in circuits?
Definition
 Resistors limit current, so when combined with cap's, they cause a slower charging up of the cap.
Term
 Potential inside of a conductor
Definition
 EP=Ed=V
Term
 Three advantages of placing a dielectric between the plates of a cap
Definition
 (1) capacitance increases by a factor of K(kappa) C=Kє0A/d(2)provides mechanical support so that the plates don't touch(3)it increases the Vmax and allows it to store more energy(you can put more volts across the cap)
Term
 Electric field inside a conductor
Definition
 Zero (because of sheilding)
Term
 Why does electric potential decrease inside of a capacitor when a dielectric is placed between the plates?
Definition
 The electric field of the capactior decreases when the dielectric is introduced because is creates its own, smaller electric field. If EP=Ed, and E decreases and d is constant, then EP decreases.
Term
 Define eV
Definition
 electron volt--it is a non-mks unit for energy that 1eV=1.6x10^-19Jthe kinetic energy that an electron gains by going through a potential difference of 1V.
Term
 Potential difference in uniform electric field
Definition
 ∆PE=-qEd
Term
 Why can an electric potential energy function be defined for the electric force?
Definition
 Because electric force is conservative force, and conservatice forces define EPE function
Term
 Resistors in series and parallel
Definition
 In series, R's Voltage adds (Vtotal=V1+V2...)In parallel, R's have an equal voltage (V1=V2=Vtotal...)
Supporting users have an ad free experience!