Electric Fields, Current, Potential Difference Flashcards
Electric field point away or to positive source charges?
Electric fields point away from positive source charges
How many charges are needed to create an electric field?
one
How many charges are needed to create an electric force?
two charges
If there is a uniform magnetic field, what is electrostatic force?
Electrostatic force and particle acceleration will be constant
When will a field do work?
Only if there is displacement in direction of electric field or opposite of electric field
What is an electric dipole?
Equal but opposite charges
If a conductor is placed in an electric field, what happens?
conduction electrons will move in response to the field
Why is there no electrostatic field inside a conductor?
There is no excess charge within a conductor
If an external electric field is brought to a conductor what happens?
free charges move to the surface and shield the interior to keep the electric field zero inside
What are equipotentials?
Potentials that are the same within the electric field
Electric potential is inversely proportional to what?
the distance
When is there no change in potential energy for a charge?
When initial and final positions are at the same potential
When moving with nature, the change in potential energy is positive or negative?
negative. Potential decreases
When moving against nature, the change in potential energy is positive or negative?
Positive. Potential increases
When is mechanical energy conserved?
if there is no friction or other forces doing work while the charge moves.
What is electric circuit?
pathway for movement of electric charge, consisting of voltage source, connecting wires, and other compounds
What is current?
Movement of charge
What is drift velocity?
slight movement of conduction electrons in a particular direction
What is the unit for current?
Amps
What is the unit for voltage/ potential difference?
Voltage
If there is voltage, what else is likely present?
current
What is another name for electormotive force?
voltage
What kind of intrinsic resistance do metals have?
low intrinsic resistance
What is the unit of resistance?
Ohm or Volts per Amp
Resistance is directly proportional to what?
Length of wire
Resistance is inversely proportional to what?
square of diameter or area of wire
What is resistivity?
expresses resistance in terms of materials intrinsic resistance
Resisitivity of conductors increases with what?
temperature
When is Ohm’s Law obeyed?
When resistance is constant and voltage is varied. If voltage is reversed, polarity must be reversed
What is Ohm’s Law?
Voltage equals Current times Resistance
What is a DC circuit?
Simple circuit that has a voltage source connecting wires to a positive terminal and negative terminal
What terminal has higher potential in a DC circuit?
Positive terminal
What terminal has lower potential in a DC Circuit?
Negative terminal
Which direction does conduction electrons drift in a DC circuit?
low to high potential or negative to postive
What is the direction of current in a DC circuit?
counterclockwise going negative to positive
In series resistors, what are the quantities of current and voltage?
Current is the same and voltage is different
In parallel resistors, what are the quantitites of current and voltage?
Voltages are the same and currents are different
What is Kirchhoff’s law dealing with voltage?
for a circuit with one battery used as voltage source, sum of voltage drops across resistors starting at positive terminal and ending at negative terminal.
What is kirchhoff’s law dealing with current?
Amount of current entering parallel combination is equal to sum of currents that pass through all individual resistors in combination
What does power for resistors equal?
Power equals Current squared times resistance
What is power dissipated by resistors equal to?
Power supplied by battery. conservation of energy
What does power equal for a circuit?
Power equals Current times voltage
What are voltmeters used for?
to measure the voltage between two points in a circuit
What are ammeters used for?
Measure current through a particular point in circuit
What is a galvonometer?
measures current using interaction between currents and magnetic fields
What is a capacitor?
pair of conductors that hold equal but opposite charges
What is the net charge of a capacitor?
zero
What are the units for capacitance?
Faraday or Coulomb per volt
What is capacitance determined by?
sizes of plates and how far apart they are
To keep voltage low would we want a capacitor of greater or lesser capacitance?
greater
What are the two uses for a parallel plate capacitor?
create a uniform electric field and store electric potential energy
Electric Fields between capacitors always point in which direction?
positive to negative
How is potential energy stored between plates?
voltage source must do work against electric field created between plates of capacitor
What does an insulator do for capacitance?
It increases
