Quiz #2 Electric Forces and Fields Flashcards
What is an electric field?
A region of influence surrounding an object with charge.
How is the direction of an electric field determine?
PLacing a small positive test charge in the electric field and identifying the direction of the electrostatic force acting on the test charge.
What is a test charge?
- The object that experiences influence in an electric field
-Needs to have a small charge and not necessarily a small mass
What are the units for electric field? What does this unit mean?
N/C. Describes the force (in N) exerted on 1 unit of charge(how much influence 1 charge has)
h
n
What is electric potential energy?
Ep
It is the energy of a charged object due to its position in an electric field.
What happens to electric potential energy when work is done against the direction of the electric field?
Ep increases
(delta) Ep>0
What happens to electric potential energy when work is done in the same direction as the electric field?
Ep decreases
(delta) Ep<0
What happens to electric potential energy when motion is perpendicular to the direction of the electric field?
No change in Ep
(delta) Ep = 0
The work done by an applied force to move a charge in the electric field ___________(1) can be determined using the _____________(2). It is equal to ____________(3) when the object is moving at a constant velocity in a frictionless environment.
(1) At a constant velocity
(2) Work-Energy theorem
(3) Electric potential energy
Need to remember to write out the entire work-energy theorem and then cross out the parts o the equation by making sure that the object is moving at a constant velocity in a frictionless environment.
What is electric potential difference?
(delta) V
A measure of the work required to move a unit of charge a specific distance in an electric field. Also referred to as voltage
When is electric potential difference when moving perpendicular to the electric field?
Zero
What is a parallel plate? How is it created?
Designed to produce a uniform electric field in the region between the plates. A battery is hooked up to two metallic plates. The battery will do work to build a negative charge of -q on one plate and leave the opposite plate with a positive charge of +q.
What is the purpose of the Millikan Oil Drop Experiment
To determine the magnitude of charge on an oil drop. Each drop is whole number multiple of a base unit of charge.
___________(1) is a factor in the motion of the oil droplet
(1) gravity
How does the apparatus for a Millikan Oil Drop experiment operate?
- An atomizer sprays charged oil droplets into the electric field.
- The voltage is adjusted until there is no motion of the drops in the vertical direction.
How does the apparatus for a Millikan Oil Drop experiment operate?
- An atomizer sprays charged oil droplets into the electric field.
- The voltage is adjusted until there is no motion of the drops in the vertical direction.
What is electric current?
The amount of charge moving past a specific point In a conductor over a certain time interval
What is electric current abbreviated with?What is electric current measured in?
- Electric curent is abbreviated with the letter I
- Measured in unit of Amps(A)
1.0 A = 1.0 C/S
What is resistance? What is resistance measured in?
Resistance(R) limits the current that flows from a specific potential difference. Resistance exists even in good conductors. Resistance is measured in units of Ohms(horseshoe)
What are the four factors that resistance is dependant on?
- Length of the conductor(L)
- Cross-sectional area of the conductor(A)
- The temperature of the conductor
- The nature of the material
What is Ohm’s law?
describes the relationship between potential difference, electric current, and resistance.
(delta) V = IR
How does resistance vary with L?
Resistance varies directly with L
How does resistance vary with A?
Resistance varies inversely with A
What happens to resistance as temperature increases?
Resistance increases as temperature increases
What is material resistivity dependant on?
Material resistivity(p) is dependant on temperature
What formula relates resistance with p, L, and A?
R = (pL/A)
What is electric power?
The rate at which electric potential energy is dissipated by a resistor
What are the two formulas needed to be memorized relating to electric power?
P = I (delta)V
P = I^2 R
P = (lql V)/ t
What is conventional current?
- Charges move from the positive terminal(area of excess charge) to the negative terminal(area of deficit charge) of a battery
- Protons move from positive to negative terminal of a battery
- Ask where a proton would move
What is electron flow?
Electrons move from negative to positive terminal of a battery.
The electric field anywhere inside of a conducting object is ________(1) even if the object is hollow.
zero
For irregularly shaped conductors, the charge density will be greater on ___________(1) of the conductor and lower on __________(2) of the conductor.
(1) sharp edges
(2) flatter parts
What are equipotential lines?
Lines of constant electric potential or voltage. They are always perpendicular to electric field lines.
Electric fields are referred to as ____________(1) because they communicate information regarding both __________(2) and _____________(3) of the field. Equipotential lines are referred to as ____________(4) because they only communicate information regarding _____________(5).
(1) vector fields
(2)magnitude
(3) direction
(4) scalar fields
(5) magnitude
