P4- Electric circuits Flashcards
How do insulators become charged?
By rubbing another insulator on it, electrons are transferred from one material to the other
When a cloth was rubbed against a rod the cloth became positively charged, why?
Negatively charged electrons were transferred from the cloth to the rod. More positive charges on the cloth
What is an electric field and when is it strongest?
The surroundings of a charged object which creates a force. Strongest when distance between charged objects is small
How does a non contact force occur?
When two charged objects exert a force on each other
What happens to…
Same charges?
Dif charges?
Same charges repel
Dif charges attract
Switch
What does it do?
How does it look?
Enables current to be turned on and off
Two circles with diagonal line between
Cell
What does it do?
How does it look?
Pushed electrons around a circuit
Big line parallel to smaller line
Battery
What does it do?
How does it look?
More than one cell
A cell with dashed line between
Diode
What does it do?
How does it look?
Allows current to pass in the forward direction
Arrow in a circle
Fixed resistor
What does it do?
How does it look?
Reduced the current
Rectangle
Variable resistor
What does it do?
How does it look?
Allows current and resistance to be changed
Rectangle with arrow through it
Light emitting diode (LED)
What does it do?
How does it look?
Emits light when current passes through it in a certain direction
Diode with arrows off it
Lamp/bulb
What does it do?
How does it look?
Emits light when current passes through it
Circle with cross in it
Fuse
What does it do?
How does it look?
Melts and breaks circuit is current is too high
Rectangle with line through it
Voltmeter
What does it do?
How does it look?
Measure potential difference
Circle with V
Ammeter
What does it do?
How does it look?
Measures current
Circle with A
Thermistor
What does it do?
How does it look?
Resistance changes with temperature
Rectangle with hockey stick
Light dependent resistor (LDR)
What does it do?
How does it look?
Resistance changes on amount of light
Rectangle in circle with arrows pointing to it
Current?
Unit?
The flow of charge around a circuit
amps (A)
Ammeter & voltmeter measures?
placed in?
Ammeter- Current, series
Voltmeter- Potential difference, parallel
Resistance
Measure of how difficult it is for current to pass through a component
Ohms law
The potential difference is directly proportional to the current when the temp is constant
How to investigate the resistance of a wire based on length?
-Set up wire, ammeter & voltmeter in a circuit
-Attach a crocodile clip to start of wire and first specified length
-Record length, current & pd
-Switch of circuit, calculate resistance
-Vary length of wire, repeat
What does a directly proportional graph look like?
Straight line through the origin
How to investigate component characteristics
-Set up ammeter, variable resistor, component & voltmeter
-Record current and pd
-Switch off power supply
-Adjust resistance & take new reading
-After 5 readings, reverse terminals to take negative values
-Take another 5 readings, plot graph
-Repeat with other components
Current-pd graph for a filament lamp
Ohmic conductor?
Increased pd..?
Increased temp..?
-Not an ohmic conductor
-As the pd increases, current and resistance increases
-If the temp increases, current and resistance increases
Current-pd graph for a diode
Ohmic conductor?
Increased current..?
In reverse direction..?
-Not an ohmic conductor
-Current only flows in one direction
-In forward direction, as current increases, resistance increases
-In reverse direction, resistance is very high
Current-pd graph for thermistors and LDRs
Ohmic conductors?
Temp/light increases..?
-Not ohmic conductors
-As temp or light intensity increase, resistance decreases
In series circuit
Current is…?
Pd is…?
Resistance is…?
Same across each component
Shared between components
Added up across all, to give total resistance
In series circuit, how to calculate..
Total current?
Total pd?
Total resis?
Same as single component
Add up pds of all components
Add up resis of all components
In parallel circuit
Current is…?
Pd is…?
Resistance…?
Shared between branches
Same across all
Total res is less than the resistor with least resistance
In parallel circuit, how to calculate..
Total current?
Total pd?
Total resis?
Add up current of all components
Same as single component
Less than the resistor with least resistance
Series circuit
Components arranged in…
Routes?
Components arranged in a single chain
Current only has one route to take
Parallel circuit
Components arranged in…
Routes?
Components arranged in branches
Current has more than one route to take
