Electricity Flashcards
define current
the rate at which charge flows
how is charge reperesented
in coulumbs (Q)
what is a delocalised electron
an electron that is loosely bonded to an atom and can therefore easily move between atoms
true or false electrons flow through a meatal to create charge
True
when components are in series will all current pass through at components in series?
yes
what is number density (n)?
the number of charge carriers per unit volume of a conductor
state the electrical current equation
I = AnVq
where:
I = current (A)
n = number density (m^-3)
A = cross-sectional area of conductor (I is directly proportional to A) (m^2)
q = charge of carriers
define potential difference
the amount of work done (energy transferred) per unit charge
what is the formula for potential difference?
V = W/Q
where:
V = volts
W = work ( J s^-1 or just Jules)
Q = charge in Columbus
what does 1 J C^-1
(Jule per coulomb) equal?
one Volt
what are volts measured with?
a volt meter connected in parallel to the circuit
True or false. p.d in each branch of a parallel combination is the same and is equal to the p.d across the entire combination
True
define Electrical power
the rate at wich work is done
What does 1 C s^-1 equal?
1 C s^-1 = 1A
what are the four formulas for electrical power?
P = W/t
P = VI
P = (I^2)R
P = (V^2)/R
where:
P = Electrical Power
W = work done (in Jules)
t = time in seconds
I = current
V = voltage
R = Resistance
what what are the si units of work done
J s^-1
what is resistance?
the opposition to the current
what will happen to the current if the resistance increces
the current will decrece
what is ohms law equation?
V/I
Where:
V = voltage
I = current
what does 1 V A^1 equal
1 ohm
what is ohm’s law?
for a conductor at a constant temp the current through it is proportional to the potential difference across it (Current is proportional to Voltage)
what is a ohmic and non-ohmic component?
an ohmic component is a component that obeys ohms law
a non-ohmic component is a component that does not obey ohms law
how does temperature effect resistance
an increase in temperature increases the resistance
and
current flowing through a conductor increases temperature
what is an LDR?
it is a Light-dependent resistor that decreases resistance with an increase in light intensity (is a non-ohmic component) (has the circuit symbol of a resistor with two arrows pointing at it)
what is a thermister
a temperature-dependent resistor that as temp increases resistance decreases (non-ohmic) (has the symbol of a resistor with an ice hockey stick over it)
what is Kirchoff’s 1st law?
the sum of the currents entering a junction always equals the sum of the currents out of the junction (I = I1 + I2 + I3 …)
what is a junction
a point where at least 3 circuit paths meet
what is Kirchoff’s 1st law a result of?
the conservation of charge
what is Kirchoff’s 2nd law?
the sum of the e.m.f’s in a closed circuit equals the sum of the potential differences (E1 + E2 = V1 + V2)
what is e.m.f?
the p.d across the battery
True or false. resistors in series are potential deviders
True
what is the formula for total resistance for resistors in series
R total = R1 + R2
True or false. resistors in parallel are current dividers
True
when you add a resistor in parallel what will happen to total resistance and current?
the total resistance will decrease increasing the current
