Electricity (circuits) Flashcards
How to work out resistance
R = V/I
Define current
The rate of flow of charge where charge is the flow of electrons
whats current measured in
amps
How to work out charge
Q (Charge(Coulombs)) = I x T (time(seconds))
how do you convert milliamps into amps?
(Your mA) x 10^-3
in parallel what rules does current follow
IT = I1 + I2 + I3
the resistance of a filament bulb ________ with potential difference.
increases
How to work out voltage
V = E/Q
define Potential difference
the electrical energy carried per unit charge
in parallel what rules does P.D follow
VT = V1 = V2 = V3
You have a coil of wire connected to a battery at both ends and an ammeter across the circuit and a voltmeter across the coil of wire. the coil is dipped in water, why?
to keep the temperature constant.
How do you calculate the total resistance of two resistors in series?
add the resistance of both of the resistors together.
RT = R1 + R2 + R3
name 4 factors that may effect the resistance of a wire
the metal used, the current flowing through it, the length of a wire, and the cross-sectional area.
What is charge measured in
coulombs
in series what rules does P.D follow
VT = V1 + V2+V3
in parallel what rules does resistance follow
RT = R1 + R2 + R3
why does the resistance of a filament bulb increase with potential difference.
it’s non-ohmic. current increases - flow of electrons increases - more collisions of electrons with atoms increase. atoms vibrate (increase K.E) increase temp.
in series what rules does resistance follow
RT = 1/R1 + 1/R2 + 1/R3
how to work out power
P =V x I
How do you calculate the total resistance of two resistors in parallel?
RT = 1/R1 + 1/R2 + 1/R3
what is ohms law
The potential difference across a conductor is directly proportional to the current through it.
Total resistance in a parallel circuit will always be ______ than the lowest resistor
less
in series what rules does current follow
IT = I1 = I2 = I3
describe the effect a variable resistor and a diode has on the current?
a diode can only change between a very high resistance (going backwards) and a very low resistance (going forwards). the variable resistor can make more subtle changes.
What is the equation for calculating efficiency
Efficiency = Useful energy output/total energy input (*100 if you want a percentage)
What is AC
Alternating Current
What is DC
Direct current
What is the difference between AC and DC
For an AC circuit the direction of flow is reversed repeatedly. However in a DC circuit it flows from the positive to the negative terminal without a change in direction.
Equation for calculating frequency
f = 1/T
What is frequency’s units
Hz
Herts
What colour is the live wire
Brown
What colour is the earth wire
Green and yellow
What colour is the neutral wire
Blue
What makes brass pins good in a plug
Hard and rust resistant
Why are the plug casings made from plastic
For insulation
What is the cable grip used for
To hold the cable firmly
What cable do you have coming out of a plug
2 core (only neutral and live) if it is double insulated (When the electrics can never come in contact with the outer casing of the device), 3 core if not.
