Unit 1.5 - Electric Circuits Flashcards
When more bulbs are added to series circuit, the current…
…decreases
When more batteries are added to series circuit, the current…
…increased
When the current increases, the lamps got…
…brighter
When the current decreased, the lamps got…
…dimmer
This is a battery, which way does the current flow:
——|l——
<—-
This is a battery, where does the current flow:
——-l|———-
—>
In a series circuit, current
Is the always the same
In a series circuit, voltage
Is different across each component. It adds up to the total voltage supplied
In a parallel circuit, current
Splits in half at each junction then combine at the end
In a parallel circuit, voltage
Always Stays the same
What creates resistance
When electrons can’t pass through the gaps between wire particles
As you increase resistance, current
Decreases
If resistance is doubled, current
Divides in half
Which two things is current proportional to
Voltage - directly
Resistance - inversely
Resistance higher in short or long wire?
Long - more particles, more frequent collisions, less electrons passing, less current, more resistance
Resistance higher in thick or thin wire?
Thin -less paths between particles, less electrons likely to pass, current decreases, resistance increases
Resistance higher in wire with a few electrons or lots of electrons?
Few electrons-less current flows with electrons, resistance is high
What are materials with no electrons called
Insulators
Resistance higher at low or high temp
High temp - particles have more energy, vibrate more, don’t get bigger, take up more room, less space for electrons to pass, less current, resistance higher
How to add up resistance in series circuit
R = R1 + R2 + R3 …
How to add up resistance in parallel circuit
1/R = 1/R1 + 1/R2
R = R3 + R4 + (1/R1 + 1/R2)
Equation connecting R, I, V
R = V/I
Example of Standard test circuit
———- |l —————
l. l
l. l
/. [\]
l. l
l———A——-X——-l
l—-V—-l
What does each of the components do in a standard test circuit
Ammeter-measures current through the component
Volt meter-measures voltage across component
Variable resistor-used to change current flowing in circuit
Component- what is tested
On a VI graph, which line has a lower resistance, steeper or not
Steeper
VI graph for filament lamp - what happens as voltage increases
More current flows in lamp causing thin wire filament to increase in temp, increasing resistance-shown by decrease in gradient on VI graph
VI graph for diode - What happens as voltage increases
A diode only allows current to flow in One Direction, Because of this current will only flow if the threshold voltage is reached, meaning V a graph will be constant at first then become steeper shortly after.
How does a diode work?
When connected forward, it has low resistance (no current). When reversed it has high resistance (current flows)
VI graph for LDR-what happens when voltage across LDR decreases
LDR is a semiconductor. Under bright light more electrons are free to carry charge, resistance is low.(steep graph)
Under dark conditions, resistance is high (less steep graph)
V I graph for thermistor-what happens as temperature increases
Resistance decreases as thermistor is a semiconductor. As the temperature increases more electrons are free to carry charge therefore decreasing resistance
Equation connecting power, energy transfer, time
P = E/t
One watt is worth
1 J/s
Equation connecting power voltage and current
P = V x I
Equation Used to calculate kWh 
kWh = P x t
Cost of electricity equation
Cost = kWh x cost per unit
