13 Circuits - 4th Form Flashcards
Why are the bulbs dimmer in the second circuit?
Voltage is shared between bulbs in series
Less voltage across each bulb therefore bulb is dimmer.
Define voltage
Energy per unit charge either supplied by a cell, or transferred to a component.
What component symbol is shown below?
Light dependent resistor
What is voltage measured in?
Volts or V
What is the voltage across a cell or power supply a measure of?
The energy transferred from chemical store electrically to the wires per coulomb
What component symbol is shown below?
bulb
What component symbol is shown below?
ammeter
Define current
- The rate of flow of charge
OR
- the number of coulombs passing a point in a circuit per unit time
(It is not the speed of the electrons!)
What happens to the total resistance and current in a circuit as more bulbs are added in parallel
Adding bulbs in parallel decreases the total resistance
V=IR
I = V / R
as resistance decreases, current increases for the same voltage
How will the current change if the resistance of a circuit is decreased for the same voltage?
current will increase
To investigate how the currect varies with voltage in a filament bulb, fixed resistor and diode you should use the cirucit below.
Why does the circuit need a variable resistor?
To vary the voltage across the component
Independent variable is voltage
Dependent variable is current
What is resistance?
- The tendency of a material to resist the flow of an electrical current.
- A measure of how much voltage is needed per amp of current.
How does the resistance vary with light intensity on a LDR?
As light intensity increases, resistance decreases
What is a volt?
1 V = 1 J/C
1 volt = 1 joule per coulomb
How does voltage related to current and resistance?
V=IR
What is true about the current in a series circuit?
Current is the same everywhere in a series circuit
What type of circuit is this? Series or parallel?
Series circuit
Only one path or branch in the circuit
What are the prongs of a plug made of brass but the wires made of copper?
Brass is strong and will not bend
Copper is a good conductor of electricity and ductile (can be drawn into wires)
What component symbol is shown below?
thermistor
How does voltage across bulbs in a series and parallel circuit differ?
Current is conserved in all circuits
Series - current is the same everywhere in the circuit
Parallel - current splits between the branches- current into a junction equals current out of a junction
What is the unit for current?
ampere / amps or A
What component symbol is shown below?
buzzer
What component symbol is shown below?
voltmeter
What component symbol is shown below?
Fuse
What component symbol is shown below?
Light emitting diode
What component symbol is shown below?
motor
Bulbs in series provide a larger resistance than bulbs in parallel
With this in mind, which circuit draws a larger current from the cell?
V = IR
I = V / R
as resistance decreases, the current increases for the same voltage
The second circuit draws a larger current from the cell, bulbs are in parallel and the total resistance is smaller than the first circuit (series circuit)
Each cell provides 3 V. In which circuit (series or parallel are the bulbs brighter?
Bulbs in parallel are brighter = both have 3V across them (brighter)
Bulbs in series have 1.5 v across each (dimmer)
Series- voltage is shared - VCell = V1 + V2
Parallel - each bulb gets the full voltage of the cell - Vcell = V1 = V2
How does current differ between series and parallel circuits?
Current is conserved in all circuits
Series - current is the same everywhere in the circuit
Parallel - current splits between the branches- current into a junction equals current out of a junction
How does the resistance of an LDR vary with light intensity?
As light intensity increases, resistance decreases
Describe what it means when 1 A is passing through a circuit
1 A = 1 Coulomb per second
The IV graph below is for an ohmic conductor…
Give an example of an ohmic conductor.
- fixed resistor
- wire (if at constant temperature)
Below is the IV graph for a….
filament bulb
Explain why the second circuit draws a lower current from the cell?
circuit with two bulbs in series - has larger resistance
V=IR
I = V/R
as resistance increases, current decreases for same voltage
What component symbol is shown below?
diode
For a wire - as temperature increases, resistance also increases.
The graph below shows the opposite.
What component is this graph for?
Thermistor
What component symbol is shown below?
variable resistor
What component symbols are shown below?
battery/two cells
&
solar cell
