Electricity Flashcards
what are the conditions for charge to flow?
a closed circuit with a source of p.d
charge equation
Q= It
what is static electricity?
build up of charge on an insulator
what is current?
rate of flow of charge
what is shock?
- p.d between student and tap
- electrons transfer from student
to the tap - static charge is discharged
what is p.d?
energy transferred between 2 points
what is resistance?
opposition to current
p.d equation
V=IR
energy equation
E=QV
what is series circuit?
a circuit with one loop
what is a parallel circuit?
a circuit with more than one loop
parallel vs series
parallel series
I - split same
V - same split
R - lower sum
relationship between R and I ?
The greater the resistance of the component
the smaller the current for a given potential difference (pd) across
the component.
resistance rp
- attach crocodile clip on 0cm on
the metre rule - attach the other clip at a fixed
distance eg. 10 cm - record the length
- close the switch and record ammeter and voltmeter readings
- open switch and move the second clip another 10 cm
- repeat those steps again for the different lengths
- calculate resistance for the lengths using V=IR
- plot a graph with your results, your line should be straight and passes through the origin
what is an ohmic conductor?
The current through an ohmic conductor (at a constant
temperature) is directly proportional to the potential difference
across the resistor. This means that the resistance remains
constant as the current changes.
what is ohm’s law?
current is directly proportional to p.d
what is TURD (resistance in thermistors)
Temp
Up
Resistance
Down
what is LURD (for LDRs)
Light
Up
Resistance
Down
IV characteristics rp
what is d.c and a.c?
- d.c= direct current
current only flows one way eg. batteries - a.c= alternating current
current constantly changes direction eg. UK mains
frequency equation
frequency= 1/T(period - time taken for one oscillation)
UK mains
230 V 50 Hz
what are transformers used for in the national grid?
step-up transformers are used to increase the p.d to 400 kV from the power station to the transmission cables; this lowers the current= less heating of the wires= less energy wasted= more efficient
step-down transformers are used to decrease, to 230 V the p.d for domestic use.
power equations
P= I²R
P= IV
what is power?
rate of energy transfer
wires in UK
Earth - stripped yellow and green + safety feature connects to the earth
Live - brown + carries a.c 230 V
Neutral - blue + 0V completes circuit
fuse - melts if temp is too high
plastic case - insulation
