5. Electricity and Magnetism Flashcards
Law of Conservation of Charge
the total electric charge of an isolated system remains constant
Conductor
material through with electric charge flows freely
Insulator
material through which electric charge does not flow freely
Coulomb’s Law
The electric force between two point charges is directly proportional to the product of the two charges and inversely proportional to square of the distance between them, and directed along the line joining the two charges. (F = k q1 q2 / r2)
Electric Field Strength (E)
Electric force per positive unit test charge (E = F/q)
Radial Field
field that extends radially (like the electric field around a point charge or the gravitational field around a planet)
Electric Potential (V)
work done per unit charge moving a small positive test charge in from infinity to a point in an electric field. (V = W/q) (V = kq/r)
Electric Potential Energy
energy that a charge has due to its position in an electric field
Electric Potential Difference (ΔV)
electric potential energy difference per unit charge between two points in an electric field (ΔV = ΔEe / q OR ΔV = W / q)
Electronvolt (eV)
energy gained by an electron moving through an electric potential difference of one volt
(1 eV = 1.60 x 10^-19 J)
Electric Current (I)
current is defined in terms of the force per unit length between parallel current-carrying conductors
Resistance (R)
ratio of potential difference applied to a device to the current through the device (R = V/I)
Resistor
device with a constant resistance (Ohmic device) over a wide range of potential differences
Ohm’s Law
The current flowing through a device is proportional to the potential difference applied across it providing the temperature is constant
Ohmic Device
one whose resistance remains constant over a wide range of potential differences (eg – resistor)
Non-Ohmic Devic
one whose resistance does not remain constant over a wide range of potential differences
Electromotive Force (emf) (ε)
Total energy difference per unit charge around a circuit
Internal Resistance (r)
resistance inside a battery that causes the battery’s terminal potential difference to be less than its emf
Ideal Ammeter
one with zero internal resistance – must be placed in series
Ideal Voltmeter
one with infinite internal resistance – must be placed in parallel
Potential Divider
two resistors placed in series that divide up the battery’s potential difference (R1 / R2 = V1 / V2)
Negative Temperature Coefficient (NTC) Thermistor
Thermistor –> sensor whose resistance depends on its temperature – increase in temperature causes decrease in resistance
Strain Gauge
sensor whose output voltage depends on any small extension or compression that occurs which results in a change of length
Magnitude of a magnetic field
ratio of magnetic force on a current carrying conductor to the product of the current and length of wire and sine of the angle between the current and the magnetic field
