Electricity Flashcards
what is a field
Physical quantity that has a value for each point in space
if a charge is positive what direction would the electric field point
away
if a charge is negative what direction would the electric field point
towards
for electrical potential energy what does it mean by conservative
only depends on start and end points not the distance travelled
An insulator means what for the charges
cant move freely through
e.g. semipermeable membrane
a conductor means what for the charges
able to move freely around
e.g. the inside or outside of the cell
if outside the cell in 0mV and inside the cells is -85mV what is the change in potential energy from the inside to the outside.
0-(-85)
= 85mV
if one cell has 0 on outside and -80mV in the inside
and another cell has +80mV on outside and 0 inside
what is the difference
No difference the both will be the same
adding capacitors in series does what to the capacitors
- reduces
- makes smaller
what type of charge does conventional current point in the direction for carriers need to flow
positive
what is the equation for ohms law
V=IR
what is the equation for resistance and resistivity
R= p (l/A)
what are kirchhoff’s 2 laws
- sum of potential charges around loop = 0
current flowing into junction is the same as flowing out
how do you calculate resistors in series
R1 + R2…
how do you calculate resistors in parallel
1/ R1 + 1/R2….
resistors in series what does it mean for the current flowing and potential difference
current flowing through all resistors is the same
potential difference across each resistor is the sum of the individual potential difference
resistors in parallel what does this mean for potential difference and current flow
current flow: resistors in the sum of individual currents
potential difference: same
what is the equation for power in electrical circuits
P=VI
what is the equation for power in resistor
P= I^2R
for AC what rule can be used
power
if there are 2 lamps what will the current flow, brightness and how much power of each lamp will the lamps use
flow and voltage is half
brightness is dimmer
each lamb uses 1/4 power
Capacitance of the membrane means
slow turn off and turn on
what did benjamin franklin find for rubbing silk on glass will the glass what charge
positive
the separation of charges in a neutral object is called what
polarisation
the force between point charges is explained through what law
coulombs
if two charges have the same sign what type of force is this
repulsive
- e.g. like charges repel
if there is more than one source charge then super position principle says you can do what
calculate the electric field due to each of the source charges individually and then sum the result
conduction in metals is due to the movement of what charge electrons - what does this mean for the current in travels in what direction to the movement of elections
negative electrons
current is in the opposite direction
small cross sectional area and long length have largest/smallest resistance
largest resistance
how do you calculate capacitors in series
1/C1+1/C2….
how do you calculate capacitors in parallel
C1+ C2…
