Electricity Flashcards
(38 cards)
write out all of the circuit symbols
- closed switch
- cell
- Indicator lamp
- Diode
- Open switch
- Battery
- Bulb
- LED
- Resistor
- Thermistor
- Ammeter
- Fuse
- Variable Resistor
- LDR
- Voltmeter
what is current
A flow of charge
state the equation for Charge and the units
Charge = Current x Time
Q=IT
charge: Coulombs (C)
current: Amps (A)
time: Seconds (s)how many milliamps in 1 amp
1000
how many microamp in 1 amp
1000,000
What is meant by potential difference
- When charge particles leave a cell (power source)
- they have a max electrical potential energy EPE
- energy is transferred from the charges onto the components
- EPE decreases
- Change in EPE= Potential difference
state the equation for Potential difference and the units
potential difference = current x resistance
potential difference= volts (V)
current= amps (A)
resistance= ohms
how many ohms in 1 megohm
1000,000 ohms
what is the relationship b/t current and resistance?
As current increases, resistance also increases:
they are directly proportional
What does the IV (I on the y-axis and V on the x-axis) graph for a fixed resistor look like?
state the characteristics of the graph
straight diagonal line going from the bottom left quadrant to the top right
- directly proportional
- linear
- ohmic
- resistance is the change in V over the change in I
state ohm’s law
the current through a component is proportional to the p.d. across it provided its temperature remains constant.
What does the IV (I on the y-axis and V on the x-axis) graph for a filament bulb look like?
A)state the characteristics of the graph at the bottom in the right quadrant
B)state the characteristics of the graph at the top in the right quadrant
Graph in the shape of an “S”: curved in the bottom left quadrant, then increasing as a straight diagonal line through (0,0) and curves again in the top right quadrant
A)-Low resistance -small V/I -Filament temp low B)-High resistance -large V/I -Filament temp high
What factor affects the resistance in a thermistor?
how does it affect the resistance?
Temperature:
As its temperature increases, its resistance decreases
What factor affects the resistance in an LDR?
how does it affect the resistance?
Light intensity/ brightness:
As the light intensity increases, the resistance of LDR decreases
what is the role of an ideal diode?
allows current to flow in one direction (shown by arrowhead)
How are ammeters connected in a circuit relative to the components in the circuit?
In series
How are voltmeters connected in a circuit relative to the components in the circuit?
In parallel
How is the current shared in a series circuit?
Current is the same everywhere
How is the current shared in a parallel circuit?
Total current is equal to the sum of currents through each branch (split evenly b/t branches)
How is the potential difference shared in a series circuit?
p.d. is shared b/t the components (not necessarily evenly)
How is the potential difference shared in a parallel circuit?
p.d. across each branch is the same
How do you work out the total resistance in a series circuit?
R(total) = R1 + R2
Total resistance is the sum of the resistances of each component
What is meant by “Power”
how fast/ the rate at which energy is converted from one form into another
State the 3 equations for power
P = E/t P = IV P = I X I X R
(current squared)
Power: watts(W) Power: watts(W) Power: watts(W)
Energy: Joules(J) current: amps(A) current: amps (A)
Time: seconds (s) voltage: volts(V) resistance: ohms
