P4 - Circuit Electricity Flashcards
A charged object creates an…
Electric field around it
A second charged object in that field experiences…
A force because of the first electric field. This is a NON-CONTACT FORCE
The closer the 2 objects in the electric field…
The stronger the force is between them
What is a Non-Contact Force?
A force that acts on an object without touching it
How to draw an electric field
Circle with plus or minus in for a positive or negative electric field
Arrows coming out of the circle in the direction that a positive charge would flow in the electric field
(If the field is negative, the arrows will be pointing inwards as opposites attract, but if the field is positive then the arrows will be pointing outwards)
How is a stronger electric field showed in a diagram?
More arrows
What happens when 2 insulating materials are rubbed against each other?
Electrons are transferred from one material to another
If 2 objects are oppositely charged, air molecules in the field between them experience…
A force towards the positively charged object and if the field is strong enough, then some electrons will be pulled from the air molecules. These electrons would then hit other air molecules causing them to also lose electrons. This causes a sudden flow of electrons between the 2 charged objects.
Draw out the components of a circuit
Positive and negative terminals
Single Cell
Battery
Open Switch
Closed Switch
Variable Resistor
Thermistor
LDR
Diode
LED
Fuse
Ammeter
Voltmeter
What does a single cell do?
Provides cell with potential difference
What does a battery do?
Provides cell with potential difference
What does an Open Switch do?
Creates a break in the circuit, so turns it off
What does a Closed Switch do?
Closes gap in circuit, so turns it on
What does a Variable Resistor do?
Can change the resistor with a slider
What does a thermistor do?
Changes resistance based on temperature
high temp. = low resistance
low temp. = high resistance
What does an LDR do?
Changes resistance based on light supply
bright = low resistance
dim = high resistance
What does a Diode do?
Allows current to flow in 1 direction only and converts AC current to DC
What does an LED do?
Converts electrical energy directly to light energy
What does a fuse do?
Breaks the circuit if a fault happens (if too much current is flowing)
What does an Ammeter do?
Measures current
What does a Voltmeter?
Measures voltage/potential difference
What is Current?
A current is a flow of charge
What charge does current have and why?
Current is negatively charged because only electrons move
The size of current is…
The rate of charge per second
What is the equation linking current, charge and time?
Charge = Current x Time
Q = I t
(Coulombs) (Amps) (Seconds)
What is charge measured in?
Coulombs
What is current measured in?
Amps
What is time measured in?
Seconds
What is Potential Difference/Voltage?
A measure of the energy transferred between 2 points in a circuit per unit charge
What is the equation linking Energy Transferred, Charge and Voltage?
Energy Transferred = Charge x Voltage
E Q V
(Joules) (Coulombs) (Volts)
As electrons flow through a circuit, the energy they carry is…
Transferred to other stores of energy
Electrons that flow through wires have to..
Push their way through lots of vibrating atoms in the metal, which causes RESISTANCE
What is Resistance?
A measure of the opposition to the charge
What is the equation linking Resistance, Current and Voltage?
Voltage = Current x Resistance
V I R
Volts Amps Ohms
A connecting wire has a…
Low resistance so that electrons can easily pass through them
The thin wire filament in a bulb has a high resistance so that…
The electrons use a lot of energy trying to pass through the wire, which is then transferred into other stores of energy such as heat and light
What does a Fixed Resistor’s graph of Voltage and Current look like?
x axis = voltage
y axis = current
straight line through 0,0
directly proportional
gradient does not change so neither does resistance
gradient = 1/R
What does a Filament Bulb’s graph of Voltage and Current look like?
x axis = voltage
y axis = current
passes through 0,0
starts flat then goes directly proportional to pass through 0,0
once passed through 0,0 continues directly proportional until it plateaus
During directly proportional section the resistance is constant, as the gradient is constant and the graph follows Ohm’s Law
When the graph is plateauing, the gradient gets shallower (1/R) so resistance is increasing and the bulb is getting hot. The graph is no longer following Ohm’s Law
What does a Diode’s graph of Voltage and Current look like?
x axis = voltage
y axis = current
when voltage < 0, the line is flat as current can only flow in one direction when using a diode. resistance is going backwards, so the current is very high
when voltage > 0, the line is still curved but has a steep gradient as there is a low resistance in the
